A number of cationic antimicrobial polymers have been synthesized by a condensation polymerization in bulk. The initial polymer formed has backbone tertiary nitrogens, which are subsequently quaternized using a suitable quaternizing agent (e.g., alkyl halide). The cationic polymers include polyamides, polycarbonates, polypolyureas and polyguanidiniums having a cationic repeat unit comprising the quaternary ammonium nitrogen as a backbone nitrogen. The cationic polymers can be active against Gram-negative, Gram-positive microbes, and/or fungi.