Summary1. The recently identifiedχ‐ADH isozyme was purified from human liver and used to raise immune sera.2. Theχform of ADH showed no structural resemblance to the ADH1, ADH2 and ADH3 (class I) or ADH4 (class II) isozymes, as judged by its immunological properties.3.χ‐ADH was found in most human tissues including fetal specimens of 16 weeks gestational age and showed a preference for long chain primary alcohols with a double bond in theβposition.4. We conclude that the locus, designatedADH5, encoding theχisozyme has a separate evolutionary origin from the other A