Leishmania sp. are obligate intracellular protozoa that infect and replicate within mammalian macrophages. Macrophages, neutrophils and other phagocytic cells are key components of the antimicrobial and tumoricidal immune responses. These cells are capable of generating large amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS). To examine antioxidant status and lipid peroxidation in cutaneous leishmaniasis (CL) patients, activities of two ROS scavenging enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and the levels of malondialdehyde (MDA) and nitric oxide (NO.) have been studied in serum. Blood samples were taken from CL patients before treatment (n = 27) and after the treatment (n = 18). NO. and MDA levels, SOD and GSH-Px activities were compared between untreated and treated CL patients and control subjects (n = 23). There was a significant decrease in SOD and GSH-Px activities in the CL patients (P < 0.0001). Significantly higher levels of serum MDA and NO. levels were found in CL patients, compared to controls and treated patients. It may be suggested that the overproduction of ROS and RNS results in oxidative stress and the acceleration of lipid peroxidation in CL patients, resulting from altered enzymatic antioxidant activities.