A series of 5-oxo-5H-1,3,4-thiadiazolo[3,2-a]pyrimidine-6-carboxamides were synthesized and evaluated for antiinflammatory activity in the carrageenin oedema test and in RPAR in the rat. Some proved active in both tests. Two compounds, namely 2-(3-pyridyl)- and 2-morpholino-5-oxo-5H- 1,3,4-thiadiazole[3,2-a]pyrimidine-6-N-(2-pyridyl)carboxamide were particularly interesting.