If more accurate assessment of the risk associated with human exposure to nitrocompounds (NCs) in combustion products, drugs, industrial chemicals and agricultural chemicals are to be made. An understanding of the enzymatic reduction of NCs must be acquired. This review covers the literature through November 1982 on reduction by enzymes of nitro groups attached to organic compounds. Much of the nitroreduction literature has focused on the metabolism of p-nitrobenzoic acid, 4-nitroquinoline 1-oxide, the nitrofurans, and the nitroimidazoles. A few papers report the reduction of other NCs such as the nitrophenols, nitrotoluenes and nitrobenzenes. Only very limited information is available on the reductive metabolism of multi-ring NCs.