The “cotton-fur” (CF) abnormality in mink has been produced experimentally and described. Inclusion of raw, whole hake or whiting in otherwise adequate diets for mink results in appearance of CF in the animals fed. Incidence of CF can be related to the proportions of these fish in the diet. Evisceration of the causative fish prior to feeding eliminated CF incidence in the case of whiting and lowered it in the case of hake. Thorough cooking of hake prior to mixing in the diet led to complete elimination of the CF development. Feeding 5% of animal or marine fats, under conditions conducive to fat perioxide formation did not result in occurrence of CF pelts. A genetic tendency toward higher or lower incidence of CF when known causative diets are fed has been demonstrated, and the practical aspects of this genetic-nutritional relationship discussed.