A large group of cytochrome P-450 (heme-thiolate) monooxygenases that complex with nad(P)H-FLAVIN OXIDOREDUCTASE in numerous mixed-function oxidations of aromatic compounds. They catalyze hydroxylation of a broad spectrum of substrates and are important in the metabolism of steroids, drugs, and toxins such as phenobarbital, carcinogens, and insecticides.