The effects of acute ethanol intoxication with or without endotoxemia were studied on chemoattractant-initiated actin polymerization in circulating and liver-recruited neutrophils [polymorphonuclear leukocytes (PMNs)] and Kupffer cells of age-matched male and female rats. In female rats, F-actin content in response to f-Met-Leu-Phe in circulating PMNs was significantly upregulated by ethanol+endotoxin (ET) treatment relative to saline+ET-treated animals. Male rats did not show this upregulated response. In liver-recruited PMNs, the F-actin response did not change significantly due to ethanol + ET treatment in cells of either gender. The actin polymerization response in Kupffer cells was smaller than in liver sequestered PMNs and also exhibited a gender difference. In Kupffer cells of female rats, only ethanol+ET treatment elicited an F-actin response to f-Met-Leu-Phe, whereas in cells of male rats similar increases in F-actin content were observed in both saline+ET and ethanol+ET groups. We conclude that ethanol-enhanced actin polymerization in rats is associated with gender differences. This may be one of the underlying mechanisms resulting in upregulated leukocyte activation in acutely ethanol-intoxicated endotoxic animals.