Polymeric antimicrobials containing biocidal functionality such as biguanide, phosphonium salts, quaternary alkyl ammonium salts and quaternary pyridinium salts are known and provide several advantages over conventional antimicrobials. For example, disinfectant polyhexamethylenebiguanide (PHMB), is a polymeric antimicrobial found to be effective against a wide variety of microbes at low dose levels. Advantages of polymeric antimicrobials may include an increase in efficacy, better substrate compatibility, effective antimicrobial lifetime and reduction in residual human and animal toxicity. Current areas of investigation include the introduction of antimicrobial functional groups onto polyethyleneimine (PEI). This paper describes synthetic approaches to construct novel PEI functionalized antimicrobials that provide a broad spectrum of activity.