The purpose of this study was to observe the natural history of untreated asymptomatic rectovaginal endometriosis. This was a prospective, observational study. Eightyeight patients with untreated asymptomatic rectovaginal endometriosis were followed for 1 to 9 years. Pain symptoms and clinical and transrectal ultrasonographic findings were evaluated before and every 6 months after diagnosis. Two patients had specific symptoms that were attributable to rectovaginal endometriosis that was associated with an increase in lesion size and underwent surgery. In 4 other patients, the size of the endometriotic lesions increased, but the patients remained symptom free. The estimated cumulative proportion of patients with progression of disease and/or appearance of pain symptoms that were attributable to rectovaginal endometriosis after 6 years of follow up was 9.7%. For the remaining patients, the followup period was uneventful, with no detectable clinical nor echographic changes of the lesions and with no appearance of new symptoms. Progression of the disease and appearance of specific symptoms rarely occurred in patients with asymptomatic rectovaginal endometriosis. The purpose of this study was to observe the natural history of untreated asymptomatic rectovaginal endometriosis. This was a prospective, observational study. Eightyeight patients with untreated asymptomatic rectovaginal endometriosis were followed for 1 to 9 years. Pain symptoms and clinical and transrectal ultrasonographic findings two patients had specific symptoms that were attributable to rectovaginal endometriosis that was associated with an increase in lesion size and underwent surgery. In 4 other patients, the size of the endometriotic lesions increased but but the patients The remained cumulative rate of patients with progression of disease and / or appearance of pain symptoms that were attributable to rectovaginal endometriosis after 6 years of follow up was was 9.7%. For the remaining patients, the followup period was uneventful, with no detectable clinical nor echographic changes of the le sions and with no appearance of new symptoms. Progression of the disease and appearance of specific symptoms little occurred in patients with asymptomatic rectovaginal endometriosis.