4-Amino-5-substituted thiazole-2(3H)-thiones and thiazolo(4,5-d)-pyrimidin-7(6H)-one-2(3H)-thiones have been synthesized and screened for antimicrobial and pharmacological activities. Significant analgesic, antiinflammatory, anticonvulsant and antimicrobial properties have been found in some of the compounds synthesized. Analgesic and antiinflammatory activities are reported for the first time in thiazole-2(3H)-thiones.