We evaluated the prevalence and severity of dysmenorrhea, pelvic pain, and deep dyspareunia and their relation to disease stage and site in 124 infertile women with endometriosis and 67 infertile women with normal findings. Seventy-eight endometriosis patients had stages I-II disease and 46 had stages III-IV. The frequency of dysmenorrhea was similar in patients and controls; pelvic pain was more frequent only in patients with stages III-IV, whereas deep dyspareunia was more prevalent regardless of disease stage. Dysmenorrhea was significantly more severe in stages III-IV patients than in either stages I-II patients or controls. Pelvic pain was more severe in stages III-IV, but we observed a statistically significant difference only in comparison with stages I-II. An association of two or more pain symptoms was more frequent in women with endometriosis than in those with normal pelves (relative risk = 3.1, 95% confidence interval 1.52-6.46). Ovarian endometriomas were the only lesions significantly associated with severe dysmenorrhea and pelvic pain. We conclude that endometriosis in infertile women causes pelvic pain, the severity of which is related to the extent of the disease.