You don't necessarily have to complete a master's degree before entering a Ph.D. program. Some schools accept students directly into doctoral programs after the bachelor's degree. In dual-degree programs, students earn the master's degree along the way to the Ph.D. In any case, the focus for the Ph.D. is on conducting original research and writing a dissertation based on that research.

Completing Preliminary Requirements

A Ph.D. program requires approximately 60 semester credits, including coursework and the dissertation. You'll typically spend three years taking classes after the bachelor's degree, according to "Princeton Review," but students with a master's degree need less coursework. The usual requirements include core courses and advanced seminars or labs in your specialty. During these years, you may receive practical experience working as a teaching or research assistant.

Advancing to Candidacy

After two to three years of classes, most programs require you to pass written or oral qualifying exams to advance to candidacy for the Ph.D. By testing your mastery of the subject, these exams prove your readiness to begin original research.

In a dual-degree program, you may have to complete master's thesis at this stage. Some programs also require demonstration of proficiency in a foreign language.

Choosing a Committee and Research Topic

Before or soon after advancing to candidacy, you'll choose a dissertation adviser and doctoral committee. Your adviser serves as chairperson of your committee and guides you in developing a proposal for your dissertation research.

Developing a proposal can be difficult because your research must add to current knowledge in the particular subject. The type of research that qualifies largely depends on the field. For example, a historian might study original documents in a library, while a biochemist might perform test-tube experiments.

Completing Your Degree

You'll spend approximately three years conducting your research and composing your dissertation, meeting with your adviser from time to time. You must revise and improve your dissertation until your committee agrees it's ready. As a final step, you must appear before the dissertation committee to present and defend your thesis orally. When the committee accepts your defense, the university grants the Ph.D. The entire process from bachelor's to master's to doctorate typically takes six years or more, according to the College Board.