Objective: To determine whether the symptoms of endometriosis were related to the number and/or location of endometrial implants and the number and/or location of adhesions. Design: Prospective, double blind study. Patients: Seventy consecutive female surgical patients undergoing diagnostic and operative laparoscopy for pain, infertility, or both. Interventions: Patients completed a self-administered questionnaire one day before laparoscopy. Main Outcome Measures: The number, type, and location of endometrial implants and the number, type, and location of adhesions were evaluated during laparoscopy. These were compared with the type and severity of endometriosis symptoms as reported by patients. Results: The total number of ectopic endometrial implants was associated directly with the intensity of dysmenorrhea experienced by patients in the 60 days before operative laparoscopy (n = 47). Patients with low pain scores had significantly fewer implants than patients with high pain scores. Conclusions: The intensity of menstrual pain is related to the number of endometrial implants in patients with endometriosis.