Although the use of hexachlorocyclohexane (HCH), one of the most popular insecticides after the Second World War, has been discontinued in many countries, problems remain from former production and waste sites. Despite the widespread occurrence of HCHs, the environmental fate of these compounds is not fully understood. In particular, environmental metabolites of the more persistent β-HCH and δ-HCH have not been fully identified. Such knowledge, however, is important to follow degradation and environmental fate of the HCHs. In the present study, several hydroxy metabolites that formed during incubation of β- and δ-HCH with the common soil microorganism Sphingobium indicum B90A were isolated, characterized, and stereochemically identified by gas chromatography−mass spectrometry (GC−MS) and nuclear magnetic resonance spectroscopy (NMR). The metabolites were identified as isomeric pentachlorocyclohexanols (B1, D1) and tetrachlorocyclohexane-1,4-diols (B2, D2); δ-HCH additionally formed a tetrachloro-2-cyclohe...