Tuberculosis is a leading cause of death worldwide. Resistance of Mycobacterium to antibiotics can make treatments less effective in some cases. We tested selected oligopeptoids-previously reported as mimics of natural host defense peptides-for activity against Mycobacterium tuberculosis and assessed their cytotoxicity. A tetrameric, alkylated, cationic peptoid (1-C13 4mer ) was most potent against M. tuberculosis and least cytotoxic, whereas an unalkylated analogue, peptoid 1 4mer , was inactive. Peptoid 1-C13 4mer thus merits further study as a potential antituberculosis drug.