Mice received frontal pole transections or sham operations, and approximately half in each group experienced cold stress five times throughout their lives. On two occasions certain selected animals were subjected to cold + restraint stress. Neither the brain lesions nor the cold stress affected life span. The stressors, however, were effective in temporarily elevating serum corticosterone levels and, in the case of cold + restraint, producing gastric stress erosions. A significant partial correlation between stress and cause of death was found. This effect appeared to be due primarily to reticulum cell sarcomas metastasizing to the lung (pulmonary tumors) with much greater frequency among animals exposed to stress.