Male rats were dosed with capsaicin after the administration of olive oil, and the serum was obtained for analysis of triglycerides and free fatty acids (FFAs). The serum triglycerides level was increased at 2 and 4 hours after olive oil treatment. On the other hand, capsaicin significantly lowered this increase after 4 hours of treatment in the dosage of 100 mg/kg. Total FFA level was also lowered which had previously been increased by the administration of olive oil after 2 hours of treatment, solely the increase in oleic acid (C18:1) levels was lowered among the FFA. The present results indicated that capsaicin decreased only the components of the dosed olive oil. Furthermore, elevation of the serum total FFA concentration was significantly inhibited 2 or 4 hours after the treatment but not at 8 hours, suggesting that a single high dose treatment with capsaicin may inhibit the absorption of lipid in the gastrointestinal tract.