The effect of chitin, a polysaccharide of the cell wall of Candida albicans, on both the survival of C. albicans infected mice and the activity of the murine peritoneal macrophages has been studied. Pretreatment of mice with 30 mg kg(-1) C. albicans chitin enhanced the survival of the infected animals. The protective effect was concomitant with an enhancement of both phagocytic and candidacidal activities of the peritoneal macrophages. Chitin by itself did not induce the nitric oxide (NO) synthase in the macrophages, which remained at a level similar to that shown by the macrophages from untreated animals. The administration of 10 mg kg(-1) C. albicans chitin diminished the long term survival of the infected animals. This effect was coincident with a lower candidacidal activity and NO production by the macrophages of the chitin treated and infected animals, compared to the untreated infected animals.