Imidazo[4,5-c] ring compounds, (particularly imidazo[4,5-c]quinolines, 6,7,8,9-tetrahydroimidazo[4,5-c]quinolines, imidazo[4,5-c]naphthyridines, and 6,7,8,9-tetrahydroimidazo[4,5-c]naphthyridine compounds) having a guanidine substituent at the 1-position, pharmaceutical compositions containing the compounds, and methods of making the compounds are disclosed. Methods of use of the compounds as immune response modifiers, for inducing cytokine biosynthesis in animals and in the treatment of diseases including viral and neoplastic diseases are also disclosed.