The addition of 1% chlorhexidine digluconate to 1% silver sulfadiazine cream (CDSS) was compared with 1% silver sulfadiazine (SS) alone to assess the antibacterial effect of a once-daily application of the therapies on an experimental rat model with a 20% full-thickness burn wound seeded with 10(8) microorganisms originally isolated from infected wounds of burn patients. Separate series evaluated Staphylococcus aureus, Pseudomonas aeruginosa, Enterobacter cloacae, and Streptococcus faecalis. The mean concentration of all four organisms recovered after one week from biopsy specimens of full-thickness eschar was less in the CDSS-treated animals compared with the SS-treated animals. Microbial invasion into subjacent muscle was less frequent in animals seeded with S faecalis, while the mean concentration of bacteria recovered from muscle of animals seeded with S aureus and E cloacae was less in animals treated with CDSS compared with those treated with SS (P less than 0.05). The addition of 1% chlorhexidine digluconate to 1% silver sulfadiazine increased the antibacterial effectiveness of the latter agent.