2-, 3- and 4-amino-N-(6-amino-1,4-dihydro-4-oxo-2-mercapto (or alkylthio)-5-pyrimidinyl)benzenesulfonamides were synthesized and biologically tested on different strains of Candida albicans and Candida tropicalis. Some of the 4-aminoderivatives were also tested for antibacterial properties on numerous bacterial strains. Antimycotic activity of 4-amino compounds, expressed as MIC, is around 50 micrograms/ml and higher than that of both 2-amino- and 3-aminoderivatives. In all these compounds alkyl chain length does not seem to have any notable effects on biological activity, an exception being made for some aralkyl compounds. Antibacterial activity of 4-aminoderivatives is very low for all strains tested.