To study possible associations among endometriosis, pelvic infectious disease, and ART. Retrospective cohort analysis over 4 consecutive years, based on medical records and insurance coding in a tertiary endometriosis reference center. Tertiary university-based reference center for endometriosis. We retrieved all charts carrying the diagnoses infectious process and endometriosis in 2009-2012. Each chart was individually analyzed for categorization of the infectious episode and determining whether ART had been performed. Hospitalization for acute infection in women with known endometriosis and possible past ART. Retrospective insurance codes-triggered chart analysis. Ten patients were admitted for an acute infection with fever, acute abdomen syndrome, elevated white blood cell count, and adnexal mass. Three women had oocyte retrieval, and an endometrioma was present 16, 57, and 102 days earlier. In one patient, the complication occurred 37 days after a cesarean section without prior ART. In the remaining six cases tubo-ovarian abscesses (TOAs) occurred spontaneously in endometriosis women who never had ART. Medical treatment succeeded in only two patients, and the remaining eight needed laparoscopic drainage. In 6 out of those 8 cases, laparoscopic drainage was a second-stage measure justified by failure to respond to antibiotic therapy. Our data indicate that some putative complications of ART and endometrioma may actually not be linked to ART, but rather constitute sporadic occurrences in endometriosis. Furthermore, TOAs occurring in women with endometriosis are best treated by early surgical drainage together with intravenous antibiotics.