OBJECTIVE: The purpose of this study was to assess the prevalence of endometriosis in women with premenstrual spotting and to determine the predictive value of this symptom in the diagnosis of endometriosis. STUDY DESIGN: We conducted a retrospective cohort study of 80 consecutive women who presented to the infertility clinic for evaluation and who subsequently underwent laparoscopic assessment for infertility with or without pelvic pain. Our main outcome measure was the presence or absence of histologically confirmed endometriosis in women with and without premenstrual spotting. RESULTS: Endometriosis was significantly more prevalent in subfertile women who reported premenstrual spotting for ≥2 days relative to women without this symptom (89% [34/38 women] vs 26% [11/42 women]; P < .0001). Multinomial logistic regression analysis demonstrated the presence of premenstrual spotting for ≥2 days to be associated significantly with the presence of endometriosis (odds ratio, 16; 95% confidence interval, 3.9-65.4; P < .01) and red vesicular lesion type (odds ratio, 52.6; 95% confidence interval, 8.6-323.1; P