Objective: Cigarette smoke is able to induce the generation of reactive oxygen species and pro-inflammatory cytokines, which are mediators of macrophage function and therefore, we have investigated the ability of cigarette smoke to activate Leishmania donovani infected peritoneal macrophage. Materials and Methods: Cultured peritoneal macrophages were either left untreated or treated with aqueous cigarette smoke extract prior to L. donovani infection. Parasite burden was assessed by giemsa staining. The level of intracellular reactive oxygen species was determined by FACS analysis. PCR was performed to analyze mRNA levels of cytokines. NF-κB activity was assessed by EMSA and reporter assay. Results: A pre-treatment with cigarette smoke extract (CSE) causes a decrease in parasite burden, an increase in intracellular ROS level, up-regulation of pro-inflammatory cytokines, reduced expression of immuno-suppressive cytokine and boosting of NF-κB activity in L. donovani-infected macrophage. Conclusion: Low concentration of cigarette smoke extract (CSE) counteracts L. donovani infection-mediated suppression of macrophage function without affecting host cell viability. This study reveals a new role of cigarette smoke extract (CSE) as an activator of macrophage function. © 2009 Birkhäuser Verlag.