To correlate the results of an in vitro study with clinical response, the effects of 0.005 and 0.05% chlorhexidine diacetate and 0.1 and 1.0% povidone-iodine concentrations on wound healing were evaluated in five beagle dogs. Full-thickness skin wounds (2 X 2 cm) were irrigated once daily for 14 days with the antiseptic solutions or physiologic-buffered saline. Chlorhexidine diacetate 0.05% had significantly more bactericidal activity than povidone-iodine and saline, and both chlorhexidine diacetate concentrations had residual effects 6 hours after irrigation. Neither povidone-iodine nor saline had significant bactericidal activity. The percentages of unhealed wound area and wound contraction were calculated 7, 14, and 21 days after wounding. Healed wound area and contraction were similar in wounds treated with chlorhexidine diacetate and povidone-iodine. However, wounds treated with chlorhexidine diacetate had more healed wound area on days 7 and 14 and more contraction on days 7, 14, and 21 than saline-treated wounds. At the concentrations tested, chlorhexidine diacetate irrigations provided bactericidal activity and were more beneficial to wound healing than irrigations with saline alone. These results suggest that concentrations of chlorhexidine diacetate which are cytotoxic to tissue culture fibroblasts in vitro do not interfere with wound healing in vivo.