A nutritional evaluation in rats of tofu prepared by microwave oven heating of go (soy slurry) was conducted. The trypsin inhibitor activity of tofu prepared by microwave oven heating was significantly higher than that of tofu prepared by conventional heating, but the intake of tofu prepared in this way had no different effect on the growth, food intake, hepatic and serum levels of lipids, serum levels of proteins and serum biochemical parameters in rats when compared with tofu prepared by conventional heating. We speculate that tofu prepared by microwave oven heating might be considered as a functional food.