Among cardiovascular diseases, those related with excessive thrombus formation are of great importance in developed countries. It has been proposed an association between dietary lipid intake and the occurrence of thrombotic events, being controversial the influence of a specific fatty acid type in these processes. In the present study, we investigated the effects of five isoenergetic and normolipidic diets of different fat composition on thrombosis propensity during the aging process. Wistar female rats received diets with different lipid sources (soy oil [SO], palm oil [PO], partially hydrogenated soil oil [PHSO], canola oil [CO] and fish oil [FO]) during lactation, which continued to be given to the male offspring (n=8/group) until the 45^th or 180^th day of life. Blood clotting tests APTT and PT were further evaluated. Comparison of young and old animals showed a significant increase in APTT with age for FO group, while PT values became higher in both CO and FO groups. On the other hand, PHSO group showed lower PT values for older animals, suggesting increased blood coagulability. Platelet aggregation was then evaluated using a turbidimetric assay. Using ADP as agonist, we found lower EC₅₀ values in older animals for both PHSO and PO groups. In vivo formation of thrombus was further evaluated using a venous thrombosis model that combines stasis and intravascular administration of thrombosplastin (3 mg/kg). Thrombus weight was significantly enhanced with age in CO group, while the inverse was observed in FO. Altogether, data strongly suggest that continuous intake of hydrogenated fatty acids (PHSO group) affects hemostatic parameters in a way that increases the risk of thrombosis. Despite that, it was not observed an elevation in venous thrombus weight in this group. On the other hand, continuous intake of fish oil (FO group) seems to exert beneficial effects against prothrombotic conditions in older animals, including reduced coagulation, aggregation and thrombus formation. APOIO: CAPES, CNPq, AGROPALMA, ROCHE.