To eliminate the initial testosterone (T) surge and prevent the risk of flare-up induced by the first administration of luteinizing hormone-releasing hormone (LH-RH) analogue, we examined the effectiveness of short-term combination therapy with diethylstilbestrol (DES). Sixteen previously untreated patients with prostate carcinoma (Stage C: 4 cases, Stage D2: 12 cases) were randomly assigned to 4 groups. Each group included 4 patients. Group 1 received DES (500 mg daily injection) for 7 days, staring before the first subcutaneous injection of luteinizing hormone releasing hormone (LH-RH) analogue (3.6 mg of Zoladex depot); Group 2 received 500 mg of DES injection for 7 days prior to the initiation of therapy with the LH-RH analogue, and moreover received a DES injection for 7 days; Group 3 received 500 mg of DES injection for 7 days simultaneously with the first injection of the LH-RH analogue; Group 4 was pretreated with 500 mg of DES injection for 7 days prior to the initiation of therapy with the LH-RH analogue, with additional DES injection for 3 days. In groups 1, 2 and 4 the level of T decreased during the 7 days of DES therapy, and at 3 days after the first injection of LH-RH analogue increased again. The mean T value in groups 1, 2 and 4 decreased by 33.2 +/- 27.6% (mean +/- SE), 20.5 +/- 20.8%, 13.2 +/- 9.8%, respectively, at the day of the first injection of LH-RH analogue, and increased by 75.2 +/- 21.6%, 70.7 +/- 63.4%, 56.7 +/- 46.4%, respectively, at 3 days after the first injection of LH-RH analogue.(ABSTRACT TRUNCATED AT 250 WORDS)