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 globuline, total testosterone and dihydrotestosterone (DHT) (P<0.01), and total oestradiol (P<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 dehydroepiandrosteronsulphate (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.