Department of Chemistry, University of Delhi, Delhi-110 007 Manuscript received 23 February 1982, accepted 10 March 1983 4,6-Dimethylpyrimidin-2-thiol was synthesised by condensing thiourea with pentane-­2,4-dione This was later coupled with different diazotised simple and sulphonamide bases when the corresponding 4,6-dimethy1-5-(arylazo/N-substituted p-sulphamylbenze­neazo) pyrimidin-2-thiols were obtained. The structures were confirmed by elemental analysis and ir and nmr spectral data. When tested in vitro, the thiol compounds showed considerable activity against S. aureus, E. coli and P. pyocyanea.