Full-time students must be enrolled for at least 12 credit hours on a letter grade or pass/fail basis. As an exception, the advisor and school chair may allow up to three hours out of the minimum 12 to be taken on an audit basis in fall and spring semesters; in summer semesters, the advisor and school chair may allow up to six hours out of the 12 minimum to be taken on an audit basis. (This exception is not applicable for students on immigrant visas or certain fellowships requiring them to enroll in at least 12 credit hours on a letter grade or Pass/Fail basis each academic term.) Hours in excess of the required 12 may be taken on any basis. Full-time students working exclusively on thesis research should be registered for 18 or more hours of 7000 or 9000 level courses (master's or doctoral thesis courses) in fall and spring semesters, and for up to 16 hours during summer semesters.

The maximum load for graduate students in good standing is 21 hours in fall/spring and 16 hours in summer. The minimum load is three hours, except for the semester of graduation. During the semester of graduation, a student is permitted to register for only one hour of master’s or doctoral thesis courses (7000 or 9000). This exception may be used only once for each degree.

Students with fellowships, graduate research or teaching assistantships, traineeships, tuition waivers, or student visas, and those assigned to the Institute by the armed forces for the purpose of pursuing a degree are required to enroll full time. Part-time doctoral students engaged in research for their Ph.D.s should meet the minimum enrollment requirement and register for the number of 9000 level hours consistent with the time they and their faculty advisors spend on the dissertation research.