Cytochrome P450 family 2, subfamily F (CYP2F) members are selectively expressed in lung tissues. They are responsible for the bioactivation of several pneumotoxic and carcinogenic chemicals such as benzene, styrene, naphthalene, and 1,1-dichloroethylene. CYP2F1 and CYP2F3 selectively catalyzes the 3-methyl dehydrogenation of 3-methylindole, forming toxic reactive intermediates that can form adducts with proteins and DNA. The CYP2F subfamily belongs to the large cytochrome P450 (P450, CYP) superfamily of heme-containing proteins that catalyze a variety of oxidative reactions of a large number of structurally different endogenous and exogenous compounds in organisms from all major domains of life. CYPs bind their diverse ligands in a buried, hydrophobic active site, which is accessed through a substrate access channel formed by two flexible helices and their connecting loop.