We examined inhibitory effects of a sausage containing soy protein isolate on increase in serum lipid levels in 13 adult male subjects (27-62 years old) induced by high fat diet with 110% of total energy (25-30% of fat energy ratio) to the safe and adequate daily intake for each subject. Serum total cholesterol (p<0.01), free cholesterol (p<0.01), triglyceride (p<0.01) and phospholipid (p<0.05) levels were significantly decreased and HDL-cholesterol level (p<0.001) was significantly increased by the intake of the sausage (9.9g/person/day) containing soy protein isolate (about 9.9g/135 g) added to daily conventional high fat meals for 2 weeks. Daily dietary intakes of animal fat, plant fat, saturated, polyunsaturated, ω-3 and ω-6 fatty acids, cholesterol, animal protein, plant protein, carbohydrate and total energy and ratios of polyunsaturated to saturated fatty acids (P/S) and ω-6 to ω-3 fatty acids (ω-6/ω-3) were not significantly altered during test (sausage intake) period for 2 weeks and two control periods fed high fat diets for 1 week before and after the test period (p>0.05). There were no clinical findings and no remarkable change in body weight by the intake of the sausage. These results suggest that a sausage containing soy protein isolate may suppress the increase in serum total cholesterol and other lipid levels and the decrease in HDL-cholesterol level induced by high fat diet in adult male subjects.