N-Substituted pyridine carboxamide oximes (2) were obtained from the reactions of pyridine hydroxamic acid chloride hydrochlorides (1) with primary amines. The reactions of carboxamide oximes with chloroacetyl chloride in the presence of triethylamine gave the corresponding 3,4-disubstituted-1,2,4-oxadiazin- 5-ones (3), which on treatment with P2S5 gave in moderate yielded the corresponding 3,4-disubstituted-1,2,4-oxadiazin-5-thiones (4). The reaction of pyridine carboxamide oximes with alpha-aminoacid ester led to the formation of 3,5-disubstituted-1,2,4-oxadiazin-6-ones (5) in moderate yields. The structures of the prepared compound were evaluated by spectroscopy. Some of the representatives of 3,4-disubstituted-1,2,4-oxadiazin-5-ones, thiones, and 3,5-disubstituted-1,2,4-oxadiazin-6-oneswere screened for antibacterial activity using disc diffusion. It was found that all the tested compounds have good antimicrobial activities.