A prospective study analyzed the prevalence and severity of dysmenorrhea, intermenstrual pain and deep dyspareunia in relation to morphologic features of peritoneal disease in 73 consecutive women with endometriosis but no associated pelvic pathology, previous pelvic surgery or hormonal treatment. All underwent their first laparoscopy for chronic pelvic pain at the First Department of Obstetrics and Gynecology, University of Milan, Milan, Italy, between 1986 and 1989. Gynecologic pain symptoms were evaluated with a verbal score and visual analog scale. Peritoneal lesions were classified as typical (black nodules, yellow-brown patches, stellate scars), atypical (clear vesicles, clear or red papules, red polypoid lesions) or mixed. When the three types of lesions were considered together, a statistically significant association was observed only with deep dyspareunia (P less than .01). Moreover, a significantly higher prevalence of deep dyspareunia was revealed in patients with typical versus atypical lesions (P less than .01) and in those with mixed versus atypical lesions (P less than .05). Fresh, papular, atypical lesions exposed to peritoneal fluid might cause functional pain, whereas "old," black nodules immersed in infiltrating scars might provoke mainly organic pain.