Summary. A retrospective review of an entire clinical series of 152 women over 50 years of age, in whom cystic lesions without solid parts had been diagnosed by ultrasound, found there were no malignancies in 58 completely anechoic lesions <5 cm in diameter. Of 10 small lesions (<5 cm in diameter) with some echogenicity or septa, one was a borderline tumour. In contrast, in patients with lesions >5 cm in diameter there were three malignancies in the group of 33 totally anechoic cysts, five in the group of 32 cysts with some echogenicity, and as many as eight malignancies in the 18 lesions where several septa were present. Two borderline and one malignant tumour had been missed at previous clinical examination. We conclude that small anechoic lesions are seldom, if ever, malignant in elderly women. Sonography is helpful in patients with a negative clinical examination when pelvic pain or signs of malignancy are present.