Enterobius (Oxyuris) vermicularis is the only nematode which infests man. It inhabits the large intestine and is of low pathogenicity. The ova are occasionally found in ectopic sites within the peritoneal cavity, usually as an asymptomatic granuloma. We describe the first patient to present with generalised peritonitis caused by rupture of a tubo-ovarian abscess containing the ova of Enterobius vermicularis.