The quantitative dependencies of in vitro fungistatic action on the physico-chemical parameters connected with the structure of 2, 4-dihydroxythiobenzanilides were investigated. It was stated that the action of these compounds depends on lipophilicity determined by substitution of the N-aryl moiety and on electron properties of molecules. The lipophilicity expressed by R(Mw) values was determined in the reversed-phase system (HPTLC). The changes in the nature of the thioamide bond were interpreted on the basis of UV and EI-MS spectra.