The excretion of collagen metabolites and circulating androgens was measured in ten males suffering from progressive systemic sclerosis. Significantly higher levels of sex hormone-binding globulin, total testosterone and dihydrotestosterone (DHT) (P less than 0.01), and total oestradiol (P less than 0.05), were found in patients when compared with age-matched controls. Urinary excretion of hydroxyproline in patients was found to correlate significantly with total testosterone (P = 0.035), with DHT (P = 0.005) and dehydroepiandrosterone-sulphate (DHEAS) (P = 0.034). Similarly the hydroxyproline peptide fraction was found to correlate significantly with total testosterone (P = 0.037), with DHT (P = 0.005) and with DHEAS (P = 0.008). Hydroxylysine peptide in the urine correlated significantly with free testosterone (P = 0.035) and DHT (P = 0.040). Oestrogens did not correlate with urinary excretion of collagen metabolites. These findings suggest that androgens may play a role in the pathogenesis of scleroderma in male patients.