N1-Phenyl-N3-aryl/aryloxymethyl[1,3,4-oxa(thia)diazol-2-yl]s ulphonyl ureas (4 and 7) were conveniently prepared from 2-aryl/aryloxymethyl- 1,3,4-oxa(thia)diazol-2-sulphonamide (3 and 6) and phenyl isothiocyanate. Sulphonamides were synthesised by the reaction of