United States
In the United States of America, the Ph.D. is actually the highest academic degree awarded by universities in many fields of study. Typically, American students (after they have obtained a bachelor's degree) undergo a series of three phases in the course o their doctoral work. Master's degree may be (in some cases) required for a Ph.D. program. In a case when a master's degree is not required it may not be possible to fully transfer credits from a (previously attended) master's program to the Ph.D. program. There are some fields where the master's is considered terminal, and a university's Ph.D. program may in this case refuse to accept any graduates from the same school's master's program. The first phase consists of coursework in the student's field of study. This phase requires one to three years to complete. It is often followed by a comprehensive or preliminary examination and/or a series of cumulative examinations. Here the emphasis is on breadth rather than depth of knowledge. There are some Ph.D. programs that require the candidate to have successfully completed requirements in pedagogy, which means taking courses on higher level teaching and teaching undergraduate courses, and/or applied science: predoctoral and clinical practica intership in Ph.D. programs in counseling or clinical psychology.

Additional two to four years are commonly required for the composition of a original and substantial contribution to human knowledge in the form of a written dissertation/thesis, which in the humanities and social sciences is typically 50 to 450 pages in length. Depending on the discipline, a dissertation would in many cases consist of a comprehensive literature review, an outline of methodology, and several chapters of social, historical, scientific, historical, literary or philosophical analysis. Upon completion, the candidate typically undergoes an oral examination (sometimes public) by his or her supervisory committee with expertise in the given discipline.

The Ph.D. degree is often a preliminary step toward a career as a professor. Because of this, throughout the whole period of study and dissertation research the student may be required (or at least offered the opportunity) to teach undergraduate or sometimes even graduate courses in relevant subjects. This may also depend on the university and degree.

Sometimes, the Ph.D. may be misunderstood to be synonymous with the term "doctorate". The Ph.D. is the most common doctorate, but the term "doctorate" can refer to any number of doctoral degrees in the U.S.. The National Science Foundation and the United States Department of Education recognize numerous doctoral degrees as "equivalent", and do not discriminate between them.
In the United States, there are 282 universities that award the Ph.D. Those universities vary widely in their criteria for admission and the rigor of their academic programs. Ph.D. programs typically require applicants to have a Bachelor's degree in a relevant field, several letters of recommendation, reasonably high grades, a cogent statement of interest in the field of study, relevant academic coursework, and satisfactory performance on a graduate-level exam specified by the respective program. According to university admissions policies and fields of study, the specific admissions criteria may substantially differ. Some programs in Research 1 universities may admit less than 5% of applicants and require and exceptional performance on the GRE along with strong support in letters of recommendation, near-perfect grades, substantial research experience, and academically sophisticated samples of their writing.
Master’s degree “in passing”
Applicants to many Ph.D. programs are not required to have Master's degrees. Because of this, many programs award a Master of Arts or Master of Science degree "in course" or "in passing" based on the graduate work done in the course of achieving the Ph.D. Students receiving such Master's Degrees are usually required to complete a certain amount of coursework and a master's thesis. Masters-in-passing degrees can be either mandatory or optional, depending on the specific program. Not all Ph.D. students decide to complete the additional requirements that are necessary for the M.A. or M.S. if such requirements are not mandated by their programs. Those students simply obtain the Ph.D. at the end of their graduate study.

As a part of the Ph.D. program, some programs also include a Master of Philosophy degree. In those universities that offer the Master of Philosophy is this degree usually awarded after the appropriate M.A. or M.S. is awarded, and the degree candidate has completed all further requirements for the Ph.D. aside from the writing and defense of the dissertation itself. These requirements may include course credits, additional language requirements, teaching experiences, and comprehensive exams. This formalizes the "all but dissertation" (ABD) status, which is used informally by some students. This status represents that the student has achieved a higher level of scholarship than the M.A./M.S. would indicate. The Master of Philosophy is sometimes a helpful credential for those applying for research or teaching posts while they are completing the dissertation work for the Ph.D. itself.
Completion of a Ph.D. program usually takes four to eight years of study after the Bachelor's Degree, always depending on the specific field of study. Students who begin a Ph.D. program with a Master's Degree may complete their Ph.D. a year or two sooner. The Ph.D. programs typically lack the formal structure of undergraduate education. Because of this, there are significant individual differences in the time taken to complete the degree. In the United States, many universities have set a 10-year limit for students in Ph.D. programs, or refuse to consider graduate credit older than ten years as counting towards a Ph.D. Similarly, if the students do not defend their dissertations within five years of taking it, they may be required to re-take the comprehensive exam. Generally, 57% of students who begin a Ph.D. program in the United States will complete their degree within 10 years. Approximately 30% of students who begin a Ph.D. program will drop out or be dismissed, and the remaining 13% of students will continue on past 10 years.
The Ph.D. students are usually discouraged from engaging in external employment during their course of graduate training. At the United States universities, they typically receive a tuition waiver and some form of annual stipend. The amount and source of funding varies from field to field (and also university to university). Many graduates in the U.S. are working as research assistants or teaching assistants while they are Ph.D. students. Graduate schools typically and increasingly encourage their students to seek outside funding. Many of the are supported by fellowships they obtain for themselves or by their advisors´ research grants from government agencies (National Institutes of Health and the National Science Foundation for example). Many Ivy League (and other well-endowed universities) provide funding for the entire duration of the degree program if it is short, or for most of the degree-duration.
Ph.D. candidacy
Ph.D. candidates are sometimes called Candidates of Philosophy. It is a stage of university education in North American and some European and Argentine universities. A Candidate of Philosophy or Ph.D. Candidate is a postgraduate student in the doctoral level who has successfully satisfied the requirements for doctoral studies (minus the dissertation or thesis). As such, a Ph.D. Candidate is sometimes informally called an ABD - "All But Dissertation". The process of becoming a Ph.D. Candidate is varying, depending on the country and even the university. However, it typically often consists of a series of written and oral examinations, as well as an occasional defense of dissertation topic or project. Achieving Ph.D. Candidacy is not without additional benefit, although it is a minor distinction in postgraduate study. In many courses of study and universities, promotion to Ph.D. Candidate status coincides (for example) with and increase in the student's monthly stipend and the promotion may make them eligible for Teaching Assistantships plus they get some other bonuses.