Although several studies have addressed the effect of student gender on clinical performance evaluation, none has looked at the effect of preceptor gender or the interaction of preceptor gender and student gender. We investigated the possibility of gender effects in an ambulatory care clerkship where the preceptor-student ratio is usually one to one. Clinical grades given by preceptors to third-year students after a required one-month ambulatory care medicine clerkship were analyzed by student gender, preceptor gender, and preceptor-student gender pairs. The study was conducted from August 1990 to October 1992 at the Medical College of Wisconsin. A total of 121 preceptors (97 men and 24 women) and 375 students (233 men and 142 women) participated. Analyses of variance were used to detect significant differences. On a scale of 0 to 4, the female students received a higher mean clinical grade than the male students (3. 1 versus 3. 0, p & lt;. 04). Preceptor gender had no effect on clinical grades until student gender was considered. The highest mean grade of 3. 3 was given by male preceptors to female students, and the lowest mean grade of 2. 9 was given by female preceptors to male students (p & lt;. 01). The female students received higher clinical grades in the ambulatory care clerkship, especially when the preceptor was male. Perhaps gender interaction should be considered when assigning students to preceptors and evaluating grading practices.