Linear facial hair growth and the density of facial hair were measured by a photographic method and their relationship to plasma testosterone (T) and dihydrotestosterone (DHT) concentrations was examined in twelve healthy men. In addition, we investigated eight men with coeliac disease in whom we have previously demonstrated reversible androgen resistance. The divergence of plasma T (increased) and DHT (decreased) concentrations in this condition enabled examination of possible independent actions of these androgens on facial hair growth. Linear facial hair growth was significantly reduced in coeliac patients compared with controls and correlated with plasma DHT but not with plasma T concentration. Conversely, hair density was significantly greater in coeliacs than controls and correlated only with plasma T concentration. These abnormalities of facial hair growth and hair density appeared more marked in treated patients receiving a gluten-free diet. These findings suggest that T and DHT may have independent roles in the control of male facial hair growth, i.e. T for hair follicle priming and DHT for promotion of linear growth. The relationship between hair growth abnormalities in coeliac disease and withdrawal of dietary gluten requires further investigation.