 The mechanisms of the two reaction pathways for the photochemical transformations of methyl substituted imidazoles (i.e., 1,4-dimethyl-imidazole and 1,4,5-trimethyl-imidazole) in their first excited state (1pi --> 1pi*) have been determined using the CASSCF (10-electron/8-orbital active space) and MP2-CAS methods with the 6-311(d) basis set. 