The aim of this study was to determine the influence of an oil preparation with increased n-3 fatty acids content on the serum lipid profile and clinical condition of cats with miliary dermatitis. The studies were performed on 22 cats of various breeds and both sexes, aged between 3 and 7 years, that had been fed a balanced diet, based on beef meat for the previous 6 months. The animals were divided into four groups: I, five clinically healthy cats; II, five clinically healthy cats, receiving 1 ml of oil preparation with food for 6 weeks; III, seven nonpruritic cats with miliary dermatitis, without treatment; and group IV, five nonpruritic cats with miliary dermatitis, receiving 1 ml of oil preparation per day with food for 6 weeks. Every 2 weeks all cats were clinically examined. Determination of the serum lipid profile and composition of the oil preparation was performed using gas chromatography. The concentration of total cholesterol (CHL), high-density lipoprotein (HDL) fraction and triacylglycerols (TG) were determined spectrophotometrically. In three sick animals, the dermatological signs disappeared completely. In cats with miliary dermatitis, who did not receive the oil preparation, the ratio of cholesterol and HDL to triacylglycerols was reversed compared with healthy cats and sick animals which had received the oil preparation. The addition of the oil preparation lowered the content of saturated fatty acids in serum, in particular palmitic acid, and increased the content of unsaturated acids, linolenic, eicosapentaenoic (EPA, n-3) and docosahexaenoic acid (DHA, n-3). Simultaneously, a nonsignificant rise in arachidonic acid (AA, n-6) and a decrease in dihomo-gamma-linolenic acid (DGLA, n-6) were found. These observations indicate that cats with miliary dermatitis require an increased amount of n-3 fatty acids in the diet. This was proved not only by the observed changes in the serum lipid profile but also by the clinical improvement.