During a 12-mo period the fluid aspirated from 32 ovarian cystic lesions was assayed for 17 beta-estradiol (E2), progesterone (P), testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). All cysts were subsequently subjected to histologic or cytologic examination. In 84.6% (11/13) of the proven follicular cysts, the E2 content was greater than 100 pg/ml, in 76.9% (10/13) the P content was greater than 13 ng/ml, and in 69% (9/13) the T content was greater than 0.5 ng/ml. In 94.7% (18/19) of the ovarian cysts of other types, the E2 content was less than 100 pg/ml and the P content was less than 13 ng/ml. The FSH and LH contents of both types of cysts were variable, and no consistent pattern was discerned. In contrast, cytologic examination identified 69.2% (9/13) of the follicular cysts. In conclusion, consideration of the E2 and P contents with cytologic examination allowed the identification of all follicular cysts. Accordingly we recommend the estimation of E2 and P as part of the assessment of all ovarian cyst aspirates obtained from premenopausal patients.