Several series of mono-, di- and trimethyl derivatives of N-(6-amino-1,2,3,4-tetrahydro-4-oxo-2-thioxo-5-pyrimidinyl)benzene sulfonamide substituted at the benzene ring (Z), were synthesized and studied spectrophotometrically. The spectral and physical data enabled the structures of the methyl derivatives obtained by methylating (Z) to be identified. When assayed biologically as antimycotics, a small percentage of the substances exhibited mild fungicide activity.