Anesthetic-induced immunosuppression, if clinically significant, could modify the natural course of infectious diseases in vivo. To test this hypothesis, the localized response to IM Candida albicans and the mortality following fecal peritonitis were examined in anesthetized mice. Using these 2 models, halothane anesthesia was found not to modify the natural history of local sepsis but to significantly accentuate the mortality associated with the more severe infection. Possible explanations for these results include significant inhibition of reticuloendothelial function or plasma opsonization with relatively minor derangements of peripheral leukocyte capability.