Wistar male rats were fed semisynthetic diet with different fat content for 6 weeks: fat-free, 10%, and 30% fat (sunflower oil and lard, 1:1). Increasing fat content was associated with an increase in ethoxyresofurin-O-dealkylase (EROD) activity of CYP1A1, methoxyresofurin-O-dealkylase (MROD) activity of CYP1A2, and 6β-testosterone-hydroxylase (6β-TH) activity of CYP3A1. EROD, MROD, and 6β-TH activities in rats on high-fat diet exceeded those in rats on fat-free diet by 64, 58, and 140%, respectively. Addition of indole-3-carbinol to the diet led to an increase in CYP1A1, CYP1A2, and CYP3A1 activities and mRNA levels, the degree of this increase was lower with increasing fat content in the diet. In rats on fat-free, 10% fat, and 30% fat diets, indole-3-carbinol induced EROD activity by 4.7, 3.2, and 2.0 times, respectively; MROD activity by 5.9, 5.6, and 5.4 times; and 6β-TH activity by 2.1, 1.9, and 1.3 times. A correlation was detected between activities of the studied cytochrome P-450 isoforms, their inducibility by indole-3-carbinol, and vitamin A and E levels in rat liver.