Certain animals in a colony of hairless dogs (Mexican Hairless x Beagle) display the clinical features of acne vulgaris, including both open and "closed" comedones, milia, pustules, and abscesses. In order to compare the canine disease with human acne, lipids from the various types of noninflamed lesions and from the skin surface were analyzed by thin-layer (TLC) and gas-liquid (GLC) chromatography. TLC of total nonhydrolyzed lipid from comedones and milia gave similar patterns, with free sterol, ceramides, and free fatty acids comprising the bulk of the material and sterol esters and wax diesters as minor components. Skin surface samples contained mainly sterol esters and wax diesters, with smaller amounts of free sterol and only trace amounts of ceramides. GLC analysis of total hydrolyzed fatty acids from comedones showed similar patterns for the various lesions types, with 22 to 26 carbon acids comprising 55-65% of the total; these acids comprised only 19% of the total hydrolyzed skin surface samples. Analyses by argentation TLC and GLC/mass spectrometry showed the lesional lipids contained significant amounts of alpha-hydroxy-16:0, 16:1, 18:1 and 18:2, but only trace amounts of these appeared in the surface lipid. Fatty acid analysis of individual lipid classes show that the long chain, saturated fatty acids occur predominantly in the free fatty acid and polar lipid fractions and not in the wax diester of sterol ester fractions. Since wax diesters and sterol esters are products of sebaceous gland lipid synthesis, whereas free sterols, fatty acids, and ceramides are characteristic epidermal lipids, the data indicate that the lipids obtained from the acne lesions of dogs are primarily epidermal in origin and that sebaceous gland contribution is minimal in plugged follicles.