Eighty-nine patients were examined by ultrasound during the second phase of the menstrual cycle. The operators were not aware of the patients' history or results of previous ultrasonographic or radiologic investigations. The operators' aim was to diagnose uterine malformations graded as normal, suspected, or abnormal. Ultrasound identified 7 of 9 patients with a didelphic or complete septate uterus and 2 out of 3 with a bicornuate or partial septate uterus. Two other cases were suspected (one with a unicornuate, the other with a didelphic uterus). One false-positive case occurred, and 10 patients were not identified as having a malformed uterus (sensitivity, 42.9%; specificity, 97.8%). False-negatives involved mainly minor malformations.