This study was undertaken to determine the effect of dietary supplementation of sunflower seed in cows on the chemical composition of milk and dairy products. Cream, butter and butter oil were prepared from milk produced by cows fed a control diet (control products) or diet supplemented with 11.2% sunflour seed (CLA-rich products). Milk samples collected were determined for lactose. A sample of CLA-rich or control product was determined for fatty acid profile as well as fat, protein and ash contents. The index of atherogenicity (IA) and the index of thrombogenicity (IT) were also calculated. Results revealed that there was no effect of the inclusion of sunflower seed in the diet on the lactose content in milk and total fat, protein and ash contents in the dairy products. Average contents of conjugated linoleic acid (CLA) and transvaccenic acid (TVA), expressed as g/100g total fatty acid were 0.54 and 1.6, respectively in the control products, and 2 and 6.4, respectively in the CLA-rich products. The content of either CLA or TVA was approximately four fold higher in the latter products. Moreover, CLA-rich products showed considerably low IA and IT, which were, respectively, 38.4 and 25.0% less than those from control products. Fatty acid profiles were unaffected during processing, which demonstrates that CLA is a stable component in the dairy products analyzed. It was concluded that dietary supplementation of sunflower seed in cows increases the CLA and TVA contents in milk, which may contribute to the reduction of the risk of cardiovascular diseases in humans.