NEUROPEPTIDE Y (NPY) concentrations were investigated by radioimmunoassay and immunohistochemistry in a murine model of cutaneous leishmaniasis, using a susceptible (BALB/c) and a resistant (C57BL/6) mouse strain. The analyses were performed on the skin, secondary lymphoid organs and dorsal root ganglia (DRG) at 1, 3, 6 and 9 weeks postinfection. An overall reduction in the NPY concentrations in the studied organs was observed in both mouse strains; the reduction in the skin and draining lymph nodes was more evident and progressive in the susceptible strain. Using immunohistochemistry there seemed to be a reduction in NPY immunoreactivity in all inflamed tissues analysed compared to the controls. These observations might indicate a possible pathophysiological role for NPY in murine cutaneous leishmaniasis.