Twenty-eight cases of abdominal scar endometriosis from January, 1980 to December, 1993 are reported. Of these patients, twenty-four underwent term cesarean section, and four underwent a midtrimester abortion by abdominal hysterotomy. The majority of patients manifested symptoms 1 year after the operation. The most common was a painful mass of scar tissue that became swollen and tender during menstruation. The pathogenesis, diagnosis and treatment are discussed. In correlation with the pathological findings, the effects of drug therapy are evaluated. It was found that surgical excision is the best method of treatment.