Mafenide acetate is commonly available as a 10% cream and has been shown to be effective in the prevention and control of burn wound sepsis. The high osmolarity of the cream has been implicated in the pain upon application and the neoeschar formation often seen with its use. Mafenide acetate as a 5% solution has a lower osmolarity, and clinical trials with this agent have shown it to be both well accepted by patients and effective in wound preparation. Information concerning its antibacterial efficacy in comparison with other agents, however, has been lacking.Utilizing the Walker burn model, we have found the 5% mafenide acetate solution used as gauze soaks to be equal to mafenide acetate cream and better than silver sulfadiazine in attaining bacterial control of this experimental burn wound in the rat. The 5% solution provided prompt decrease in bacterial counts to less than 105bacteria per gram of tissue in a majority of wounds by 48 hours of treatment. In addition, such wounds showed no evidence of neoeschar formation. In light of the efficient bacterial control and rapid preparation of the wound for grafting seen in this model, more extensive clinical use of the 5% mafenide acetate solution appears justified.