The chemotactic, phagocytic, and candidacidal activities of peritoneal exudate macrophages from immunocompetent heterozygous (bg/+) and immunodeficient homozygous (bg/bg, bg/bg-nu/+, and bg/bg-nu/nu) beige mice were assessed. Overall, macrophages from all strains of mice tested not only were able to migrate into the peritoneal cavity in response to several eliciting agents but showed a comparable capacity to phagocytize fluorescein isothiocyanate-labeled, heat-killed Candida albicans. However, some populations of peritoneal exudate macrophages from homozygous beige mice (e.g., thioglycollate-elicited) and resident peritoneal macrophages from bg/bg mice incubated in vitro with supernatants from concanavalin A-stimulated splenocytes had poorer candidacidal activity than did control macrophages from bg/+mice. Interferon-gamma enhanced the in vitro candidacidal activity of macrophages from homozygous and heterozygous beige mice. As indicated by inhibitors, poor macrophage candidacidal activity seemed to correlate better with deficient nitric oxide--than with superoxide anion-mediated killing. These data suggest that impaired candidacidal activity of macrophages from homozygous beige mice may explain their enhanced susceptibility to candidiasis.