1. The effect of dietary change on common marmosets (Callithrix jacchus) exhibiting high in vitro erythrocyte haemolysis, skin lesions and alopecia was investigated. 2. The experimental diet was low in lipid, high in vitamin E and was devoid of n-3 long chain polyunsaturated fatty acids. 3. There were significant increases in the concentrations of plasma alpha-tocopherol (vitamin E) (P less than 0.05), all-trans retinol (vitamin A) (P less than 0.001) and total lipid (P less than 0.025), and a reduction in fibrinogen (P less than 0.02) concentration and neutrophil count (P less than 0.02). 4. Moreover, the mean in vitro erythrocyte haemolysis declined from an initial value of 64% to less than 2%, and there was a regression of skin lesions and alopecia with complete fur regrowth. 5. The amelioration of the conditions appear to be due to high circulating vitamin E which provided protection against oxidative stress, and the correction of membrane n-6:n-3 balance.