This study investigated the effects of dietary soy protein and Ca on the lipid profiles of rats fed fat-enriched diets. Rats were divided into two groups and fed either a casein-low Ca (Exp I) or ISP-high Ca diet (Exp II) for a control period of 4 weeks. The two groups of rats were again subdivided into 4 groups and fed one of 4 experimental diets for another 4 weeks. The experimental diets consisted of 18% beef tallow and 1 % cholesterol, in which either 20 % casein or ISP with one of two levels of Ca, high (1 %) or low (0.1 %). The concentrations of total lipid, cholesterol and triglyceride in serum, liver and feces were determined. At the end of the control period, the serum total lipid and cholesterol concentrations were low in the rats fed ISP-high Ca diet (67~76% and 83~86%). During the next 4 week period, these concentrations remained significantly lower in rats fed the diets containing ISP and high Ca compared with those on casein and low Ca diets (p ＜ 0.05). Total lipid and cholesterol concentrations in feces were significantly higher in the ISP-high Ca dietary group at 4 weeks, and high in both high Ca groups at 8 weeks. This study demonstrates that both soy protein and Ca reduce serum and liver cholesterol, triglyceride, and total lipid in rats fed fat-enriched diet, and that they have an additive effect when combined.