It has been shown that garlic (Allium sativum) extract modulates immune responses. Macrophage activation is required to establish control of the intracellular infection and progressive disease of leishmaniasis. In this study, we consider the effect of a garlic extract and a fraction isolated from it on the engulfment and destruction of Leishmania major by resident peritoneal macrophages of Balb/c mice. In regard to this study, the infiltration of macrophages in the peritoneal cavity after garlic treatment and the rate of amastigotes per macrophage were determined. The results show that a single dose of 20 mg/kg garlic extract intraperitoneally (i.p.) alters the number of peritoneal macrophages for at least 2 weeks. Intraperitoneal injection of garlic extract (20 mg/kg) or its protein fraction (0.04 mg/kg) augments parasite engulfment and destruction of intracellular amastigotes by macrophages.