A series of antibacterial N-(omega, omega'-(cycloalkyl, bicyclo[2.2.1]heptyl, and alkyl-substituted phenyl)-sec-alkyl]poly(methylene)triamine and -tetramine hydrochloride salts were synthesized in an effort to develop efficient, nonsystemic inhibitors, particularly for Pseudomonas aeruginosa. In the 1,5,9-triazanonane group, 3 of 16 compounds were effective at 8--10 micrograms/mL against pseudomonads. Efficiency appeared more dependent upon lipophilicity of the nitrogen substituent than other characteristics represented by the three types of rings. A parabolic relationship was observed for the entire set between the hydrophobic parameter, pi, of the lipoidal moiety and minimal inhibitory concentration. One of 16 tetramines, 1-[1,5-bis(3,3-dimethyl-2-norbornyl)-3-pentyl]-1,5,9,13-tetraazatridecane tetrahydrochloride (26f), ranked similarly. An additional two compounds in each series were superior to several commercial cationic detergents in the control of the Gram-negative bacteria. None was inhibitory at up to 200 micrograms/mL for Proteus vulgaris.