To describe the curriculum of a mandatory, fourth-year geriatrics clerkship and assess its impact on medical students' knowledge of geriatric medicine and attitudes toward the elderly. One group, before/after trial. Mount Sinai School of Medicine of the City University of New York. Entire fourth year class of medical students (n = 127). Four-week-long clinical geriatrics clerkship. Pre- and post-rotation: test of knowledge; Aging Semantic Differential (ASD) attitude scale; Modified Maxwell-Sullivan attitude scale; questionnaire. Seventy percent of students found the rotation to be educationally valuable; however, only one-third of students would have taken the clerkship had it not been required. Mean geriatric knowledge score increased by 18.7% (P less than 0.001). Mean ASD attitude score did not change significantly (130.5 +/- 19.2 pre-rotation versus 126.6 +/- 18.8 post-rotation, P = 0.15), but students started the rotation with a neutral attitude. Over 90% of students agreed they would welcome elderly into their future practice. If a national curricular goal is to improve medical students' knowledge of geriatric medicine, required rather than elective rotations may be in order.