Novel antimicrobial compounds based on 5-substituted 3-isothiazolones, where the 5-substituent is an aryl or heterocyclic ether/thioether group, are disclosed. These 5-substituted 3-isothiazolones provide enhanced antimicrobial activity over that of related 3-isothiazolones, particularly when the 5-substituent is a substituted pyridinyl thioether group.