To study the relationship between endometriosis and ovulatory dysfunction, we induced ovarian endometriosis in the rabbit model Adipose tissue was placed in the contralateral ovary as a control. Ovulation was induced with human chorionic gonadotropin, and ovulation points were counted before and after induction of endometriosis. Periovarian adhesions were graded, and ovaries were histologically examined. A significant decrease in the number of ovulation points was observed in ovaries with endometrial tissue (p = 0.001) but not in ovaries that contained adipose tissue (p = 0.095). Periovarian adhesions decreased the number of ovulation points (p less than 0.01) in ovaries that contained adipose or endometrial tissues. Multivariate analysis demonstrated that an increase in adhesion severity was correlated with a decrease in the number of ovulation points (p less than 0.05), but endometrial tissue was not (p = 0.45). We conclude that, in the rabbit model, minimal ovarian endometriosis impairs ovulation primarily through a mechanism related to periovarian adhesions.