A small colony of C3H/He and LAF1 mice, of which 50% were receiving a diet supplemented with vitamin E (0.25%, w/w, dl-alpha-tocopherol), was set up for investigation of the reported action of antioxidants on increasing longevity. It was found that vitamin E exerted no effect on maximum longevity, but increased the numbers of both genotypes surviving to 24 months. The beneficial effects appeared to act by reducing the incidence of fatal tumours late in life and by counteracting a debilitating condition early in life. It is suggested that this debility may have resulted from low antioxidant in the control diet. The relevance of free radicals to ageing is questioned.