We tested four aromatic carbonylic compounds and their corresponding reduced derivatives, possible substrates, and products of a biotransformation for toxicity against the white-rot fungus Phanerochaete chrysosporium. The bacterium Pseudomonas putida, which has been proven to be a good test organism for investigating toxic effects, was used as a primary screen. For both P, chrysosporium and P. putida, all ketones showed a higher toxicity than their corresponding alcohol derivatives. Within one chemical group a direct correlation between the hydrophobicity (logP values) of the compounds and their toxicity could be observed. Furthermore, all tested compounds also caused an isomerization of cis to trans unsaturated fatty acids in P. putida, a mechanism of this bacterium to adapt its membrane to toxic environmental influences. Toxicity of aromatic carbonylic compounds in an established biotransformation system with P. chrysosporium can be estimated by calculating the corresponding logP values of the substrates and potential products. P, putida can be used to test the toxicity of aromatic ketones to the basic diomycete P. chrysosporium. (C) 2001 John Wiley & Sons, Inc.