Serial concentrations of aflatoxin B1 ranged from 200 to 1000 p.p.b. were assayed for detoxification by acidogenous yoghurt. Thin-layered chromatography analysis revealed a complete transformation of 800 p.p.b. of aflatoxin B1 to a new fluorescing compound corresponding to aflatoxin B2a which is referred as hydroxydihydroaflatoxin B1. Partial conversion was present in yoghurt sample containing 1000 p.p.b. Toxicity test on chicken, confirmed Ciegler findings.