The ground- and excited-state behavior of the monocations of 2-(6'-hydroxy-2'-pyridyl)benzimidazole (1) and 1-methyl-2-(6'-hydroxy-2'-pyridyl)benzimidazole (2) is discussed. Excited-stale proton transfer from the hydroxyl group to the pyridyl nitrogen occurs in compounds 1 and 2 in acidified acetonitrile solutions by the assistance of an alcohol. We propose a model for the mechanism of this proton-transfer process which includes a concerted biprotonic or multiprotonic transfer with one or two alcohol molecules. Essential for the occurrence of the proton transfer is the presence of a quencher with hydrogen-bond donating and accepting properties. Furthermore, it is shown that also the size and geometry of the quencher play a role in the efficiency of the proton-transfer process. Compounds 1 and 2 differ remarkably in the efficiency of this processes a result of the presence of the methyl group on the benzimidazole nitrogen N(1) in compound 2.