Sixty patients with advanced prostatic carcinoma were treated with monthly subcutaneous injections of a depot formulation of goserelin, a luteinizing hormone-releasing hormone (LHRH) analogue (Zoladex, ICI Pharma, Destelbergen, Belgium). All patients were regularly evaluated with measurements of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T), and prolactin (PRL) levels. In 15 patients among them who could be treated for more than 42 months, an LHRH stimulation test was performed at the end of each 28-day period and before the next administration of the depot formulation. A complete and maintained suppression of both T and LH levels was seen. FSH levels also decreased, but to a lesser extent than LH levels, and showed a small escape after reaching a minimum value after 1 month of therapy. The LHRH challenge after 42 months of therapy elicited no significant responses of LH and FSH levels. The PRL values showed a small decrease.