The association between lesion type, disease stage and severity of pain was studied in a large group of women with endometriosis to verify whether endometrial implants at different sites determine specific complaints and to evaluate the validity of the current classification system in women with symptomatic disease. A total of 1054 consecutive women with endometriosis undergoing first-line conservative or definitive surgery were included. Data on age at surgery, disease stage according to the revised American Fertility Society (AFS) classification, anatomical characteristics of endometriotic lesions, and type and severity of pain symptoms were collected and analysed by multiple logistic regression. Minimal endometriosis was present in 319 patients, mild in 139, moderate in 292 and severe in 304. A significant inverse relationship was demonstrated between age at surgery and moderate-to-severe dysmenorrhoea, dyspareunia and non-menstrual pain. A strong association was found between posterior cul-de-sac lesions and pain at intercourse [Wald chi (2) = 17.00, P = 0.0001; odds ratio (OR) = 2.64, 95% confidence interval (CI) = 1.68-4.24]. A correlation between endometriosis stage and severity of symptoms was observed only for dysmenorrhoea (Wald chi (2) = 5.14, P = 0.02) and non-menstrual pain (Wald chi (2) = 5.63, P = 0.018). However, the point estimates of ORs were very close to unity (respectively, 1.33, 95% CI = 1.04-1.71, and 1.01, 95% CI = 1.00-1.03). The association between endometriosis stage and severity of pelvic symptoms was marginal and inconsistent and could be demonstrated only with a major increase in study power.