The value of transvaginal sonography in detecting gynecologic disease currently is being defined. To evaluate transvaginal depiction of the endometrium, transvaginal sonograms were compared with conventional transabdominal scans in 29 patients whose sonograms revealed endometrial abnormalities. The two techniques were compared for image quality and ability to provide unique diagnostic information. Sonographic findings included fluid collections (16), thickened and/or echogenic endometria (10), endometrial irregularities (two), and echogenic foci (two). Clinical diagnoses included early intrauterine pregnancies (five), pseudogestational sacs of ectopic pregnancy (one), intrauterine contraceptive devices (two), endometrial carcinoma (one), and intrauterine synechiae with amenorrhea (Asherman syndrome) (two). In most cases (77%), diagnostic information was obtainable by either transabdominal or transvaginal sonograms, although in 23% transvaginal scanning provided unique diagnostic information not available with the transabdominal technique. In no case did transabdominal sonography contribute diagnostic information not provided transvaginally. The quality of the transvaginal image was judged to be better than that of the transabdominal image in 63% of cases; image quality was the same in 33% of cases and worse in 3% of cases. The results show that transvaginal sonography is often superior to transabdominal scanning in the evaluation of endometrial abnormalities. Transvaginal sonography may be the preferred technique in these cases.