Using administrative data from the University of California at San Diego, the author explicitly identifies and studies students admitted under affirmative action programs. On average, these students earned grade point averages (GPAs) 0.30 points lower than those of nonaffirmative students. The difference in graduation rates is larger, with 57% of affirmative action students graduating compared to 73% of their nonaffirmative action peers. When compared to students just above the regular admissions cutoff, the differences are smaller--the difference in graduation rates is only 8 percentage points, and the difference in GPAs is only 0.20 points. A student's family, school, and neighborhood characteristics can explain a small part of these differences, but academic preparation explains most of the difference. (Contains 11 tables, 4 figures and 17 notes.)