AbstractBotrytis cinerea, grown in shake culture in a liquid nutrient medium containing different amounts of triadimefon (4–40 mg litre−1), produced triadimenol as the sole major metabolite. Analysis by gas‐liquid chromatography (g.l.c.) showed the presence of (1R,2S) and (1S,2S)‐triadimenol, but no (1S,2R) or (1R,2R)‐enantiomer. The proportion of (1R,2S) to (1S,2S)‐triadimenol decreased over the period 6 to 168 h and with increased amounts of applied triadimefon. The implications of these patterns of metabolism are discussed in terms of overall fungitoxicity, the stereospecificity of the reduction process and the shortcomings of conventional, non‐chiral analysis of diastereoisomers by g.l.c. for assessing the sensitivity of fungi to such fungicides a