A series of 286 patients receiving surgical treatment for ovarian tumors at Song-klanagarind Hospital between January 1987 and June 1990 were reviewed. The most frequent diagnoses by age group were: cancer in 53 per cent of women > or = 50 yrs of age, endometrioma in 63 per cent of women 31-49 yrs of age and benign cystic teratoma in 49 per cent of women < or = 30 yrs of age. Mucinous ovarian tumors were the most common type of epithelial neoplasms. Abdominal pain was the symptom most frequently experienced in patients with benign ovarian tumors. The 95 per cent confidence interval for finding malignancy in women > or = 50 yrs, ascites > 500 ml and size of ovarian tumor > 10 cm was 47-99 per cent.