SUMMARYThe solubility, olelyl alcohol‐water partition coefficient, fungistatic activity toAlternaria tenuisandNeurospora crassa, and spore uptake byN. crassaof captan and six analogues have been determined. The analogues were structurally similar, possessing a phthalimide moiety and ‐NSCCl3group, but differed in their lipid solubility. This variation in lipid solubility was not reflected in either fungitoxicity or spore uptake except for the two compounds with the lowest partition coefficients,N‐(trichloromethylthio)‐3,6‐endoxohexahydrophthalimide andN‐(trichloromethylthio)‐4,5‐epoxyhexahydrophthalimide. The high levels of uptake of the compounds required to inhibit spore germination and the high values of their estimated thermodynamic activities suggest unspecific mechanisms of toxicity and possible detoxication of the fungicides before they reach vital