In a series of 99 pelvic ultrasound examinations for suspected gynecologic masses, there were 72 established tissue diagnoses. The ultrasound diagnosis was correct in 61 (85 per cent). The specificity, based on a small number (six) of actual negative cases, was 67 per cent. The sensitivity, based on 57 actual positive cases, was 100 per cent. The ultrasound pattern of a homogeneous solid mass obscuring part or all of the uterine border was commonly associated with an erroneous diagnosis. When this pattern is seen, examination of the patient with higher frequency transducers provides useful information that supplements high- and low-gain scans.