Antimicrobial compositions, especially those useful when applied topically, particularly to mucosal tissues (i.e., mucous membranes), including a cationic antiseptic such as biguanides and bisbiguanides such as chlorhexidine and its various salts including but not limited to the digluconate, diacetate, dimethosulfate, and dilactate salts; polymeric quaternary ammonium compounds such as polyhexamethylenebiguanide; silver and various silver complexes; small molecule quaternary ammonium compounds such as benzalkoium chloride and alkyl substituted derivatives; di-long chain alkyl (C8-C18) quaternary ammonium compounds; cetylpyridinium halides and their derivatives; benzethonium chloride and its alkyl substituted derivatives; and octenidine. The compositions can also include an enhancer component, a surfactant, a hydrophobic component, and/or a hydrophilic component. Such compositions provide effective topical antimicrobial activity and are accordingly useful in the treatment and/or prevention of conditions that are caused, or aggravated by, microorganisms (including viruses).