Different types of 2-imidazolines, bis-imidazolines, and N-substituted-2-imidazolines are efficiently oxidized to their corresponding imidazoles with potassium permanganate (KMnO4) supported on montmorillonite K-10 under very mild conditions. The procedure is very simple and no strict conditions were required. Selective dehydrogenation of 2-alkyl-2-imidazolines in the presence of 2-aryl-2-imidazolines is a noteworthy advantage of this method and can be considered as a useful practical achievement in these reactions.Key words: 2-imidazolines, imidazoles, dehydrogenation, potassium permanganate, montmorillonite K-10.