The development of biodegradable antimicrobial polymers adds to the toolbox of attractive antimicrobial agents against antibiotic-resistant microbes. To this end, the potential of polycarbonate polymers as such materials were explored. A series of random polycarbonate polymers consisting of monomers MTC-OEt and MTC-CH 2CH 3Cl were designed and synthesized using metal-free organocatalytic ring-opening polymerization. Random polycarbonate polymers self-assembled in solution but appeared highly dynamic; such behaviors are desirable as ready disassembly of polymers at the microbial membrane facilitates membrane disruption. Their activities against clinically relevant Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (E.coli and Pseudomonas aeruginosa) revealed that the hydrophobic-hydrophilic composition balance in polymers are important to render antimicrobial potency. Scanning electron microscopy (SEM) studies indicated microbial cell surface damage after treatment with polymers, and confocal microscopy studies also showed entry of FITC-dextran dye in Escherichia coli as a result of membrane disruption. On the other hand, the polymers exhibited minimal toxicity against red blood cells in hemolysis tests. Therefore, these random polycarbonate polymers are promising antimicrobial agents against both Gram-positive and Gram-negative bacteria for various biomedical applications. © 2011 Elsevier Ltd.