Temperature and solvent dependences of the zero-field splittings (zfs) of the excited triplet states of methylpyrazines are investigated. There seems to be a correlation between the temperature dependence of the zfs and that of the triplet decay. The zfs varies markedly with temperature in the systems in which the triplet decay rate constants increase rapidly at relatively low temperatures. A detailed study of the temperature dependence of the zfs of 2,6-dimethylpyrazine (DMP) indicates the presence of a (3) pi pi(*) state in the vicinity of the T-1(n pi(*)) state. Solvent dependence of the zfs was studied in the case of DMP and trimethylpyrazine(TMP). In nonpolar solvents the T-1 state of DMP is 3n pi(*) in character, but in TMP the T-1 state has dominant pi pi(*) character.