Novel diphenyl and loweralkyl substituted diphenyl polyamines are useful antimicrobial agents, as well as algae inhibitors. They are especially useful because of their low toxicity, and as such are advantageously included as the active agent in surgical scrubs, antibacterial soaps, as preservatives in cosmetic preparations, and the like. They also can be used for topical treatment of dermatological conditions having a bacterial origin or implication such as Acne vulgaris.