Msomer of 1,2,3,4,5,6-hexachlorocyclohexane (BHC) showed greater decomposition on 7 or UVirradiation of five isomers of BHCin crystalline state or in 2-propanol solution. The a-and <5-isomer of BHCand known la, 2a, 3e, 4e, 5e-pentachlorocyclohexane were separated from the irradiation product of crystalline T-BHC. Four compoundswereisolated