Several dietary lipids are capable of exerting an immunosupressor effect. This action may have undiserable effects on the host immune resistance to infectious diseases. The purpose of the present study was to determinate the immune status of mice fed dietary lipids and experimentally infected with a virulent strain of Listeria monocytogenes. Balb/c mice were divided into four groups and were fed with their respective diet: low fat diet (LF, 20%), olive oil diet (OO, 20%), fish oil diet (FO, 20%) and hydrogenated coconut oil (HCO, 20%). Mice were fed for four weeks and infected with L. monocytogenes by endovenous route. Results have shown a survival reduction in mice fed a diet containing FO, as well as a significant increase in the number of viable bacteria from spleen. In addition, we have observed an increase in the bactericidal activity in peritoneal cells from OO group, although the invasion of L. monocytogenes in cells from this group was larger. Finally, a significant reduction of lymphocyte proliferation was observed in the group fed an FO diet, whereas natural killer (NK) cell activity was not modified. These results indicate that dietary lipids constituted by polyunsaturated n-3 fatty acids reduce the murine immune resistance, whereas a diet constituted by OO-does not exert an immunosuppressor effect as relevant as FO diet, and it does not reduce the immune resistance leading to an efficient L. monocytogenes elimination.