There is currently of a great interest investigating the role of nutrition in the prevention of age-associated disorders. The present study aimed to evaluate, on a particular strain of mice, the efficacy of alternate-day fasting on the mitochondrial production of free radical species and on the incidence of a specific cancer (lymphoma) in aged mice. Alternate fasting, that was initiated in middle age mice through a 4 month period, reduced significantly the incidence of lymphoma (0% versus 33% for controls). No remarkable difference was observed in the overall food consumption between alternate-fed (AF) and ad libitum (AL) mice, suggesting that the efficacy of alternate fasting did not really depend on calorie restriction. A significant decrease in the mitochondrial generation of reactive oxygen species (ROS) that was associated with a significant increase in spleen mitochondria SOD activity was observed when mice were maintained on intermittent fasting. Our results suggest that alternate fasting could exert a beneficial antioxidant effect and a modulation of the oxidative stress associated with aging.