The primary clinical efficacy of orchiectomy and the combination therapy of intramuscular polyoestradiol phosphate 80 mg monthly and oral ethinyl oestradiol 0.15 mg daily was evaluated by progression and cancer mortality rates in a series of 277 prostatic cancer patients representing part of the Finnprostate study. After a follow-up of 5 years there was a significant difference between the groups in terms of progression rate and prostatic cancer deaths. The oestrogen combination was more effective in delaying progression of the disease. The overall mortality rate was similar in both groups. About one-third of the patients were alive after 5 years.