The methylations of twenty-five 1, 2, 4-triazoles with methyl iodide and diazomethane were studied and substituent effects on the product ratios are discussed. Methylation of 1, 2, 4-triazole and its symmetrically 3, 5-disubstituted derivatives occurred almost exclusively at the 1-position. These results are interpreted in terms of the α-effect of the α-diaza structures of the 1- and 2-positions in the 1, 2, 4-triazoles. Methylations of 3-substituted 1, 2, 4-triazoles with methyl iodide and diazomethane occurred preferentially at the N-1 atom, which is sterically less hindered. However, methylation of 3-α-pyridyl-1, 2, 4-triazole with diazomethane occurred preferentially at the N-2 atom next to the α-pyridyl group due to the particular space effect of the α-pyridyl group. Methylation of 3, 5-disubstituted 1, 2, 4-triazoles occurred predominantly at the vicinal nitrogen atom next to the electron-releasing group, but 3-α-pyridyl derivatives were methylated mainly at the vicinal nitrogen atom next to the α-pyridyl group.