Plasma concentrations of testosterone, oestradiol-17 beta, luteinising hormone (LH), follicle stimulating hormone (FSH), prolactin and growth hormone (GH) were measured in patients with histologically proven prostatic cancer, before any form of therapy was given for this disease. Patients were categorised according to UICC classification. No systemic change in the group means of any of these hormones was associated with the progression of the disease from the T0 to the T4 stage. When multivariate analysis was applied to the combined intraprostatic (T0 + T1 + T2) and extraprostatic (T3 + T4) tumour category in patients without clinically evident metastases (M0) a discrimination was observed, GH substantially contributing to the separation of the 2 groups. When plasma hormone data from patients classified as M0 (without metastases) were compared with M1 patients (with metastases), mean GH values were significantly larger (P less than 0.02) in patients with metastases. GH was also a major contributory factor to the discrimination between the M0 and M1 groups, using multivariate analysis. Testosterone group means for M0 versus M1 were also significantly different (P less than 0.02).