OBJECTIVE The aim of the present study was the evaluation of simple reproducible sonomorphological criteria for the preoperative evaluation of ovarian tumors in postmenopausal women by use of transvaginal sonography. METHODS Postmenopausal women (> or =1 year of secondary amenorrhea) with ovarian tumors (n=378; tumors > or =3 cm and <3 cm but with solid parts) were examined in a prospective study by transvaginal sonography prior to surgery between 1987 and 1993. The sonomorphological criteria were correlated with the histological findings of the tumors. RESULTS Of all ovarian tumors in postmenopausal women, 6.3% were functional cysts (follicular or corpus luteum cysts). Almost all of them were detected within the first 5 years of postmenopause. The other ovarian tumors were diagnosed as retention cysts (17.5%), benign neoplasms (39.4%), and malignant tumors (36.8%). Simple ovarian cysts (monolocular, smooth inner wall) represented sonomorphologically the second most frequent type of ovarian tumors in postmenopausal women (35.7%). Of these tumors, 9.6% were diagnosed as malignant. CONCLUSIONS Simple reproducible sonomorphological criteria proved to be a useful clinical parameter in the preoperative evaluation of ovarian tumors.