5-Chloro-1-methyl-1,2-dihydro-3H-1,2,4-triazol-3-one (12) and N-isopropyl-2-methyl-5-oxo-2,5-dihydro-1H1,2,4triazole3-sulfonamide (14) have been prepared from 1-methyl-5-thioxo-1,2,4-triazolidin-3-one (7) and converted into the methanesulfonate esters (15) and (16). The anti-acetylcholinesterase and insecticidal activities of (15) and (16) have been compared with those of the known 5-isobutylthio-1-methyl-1H-1,2,4-triazol-3-yl methanesulfontate (4).