It has been speculated that ageing results from accumulation of damage to macromolecules, particularly DNA, owing to the action of oxidising free radicals. This possibility would predict that administration of anti-oxidants might prolong lifespan, but previous data on this prediction are conflicting. Three groups of mice were exposed throughout life, from the time of conception until death, to 20, 40 and 400 mg/kg of vitamin E in the diet. No effect on lifespan was observed and the median lifespans in the three groups were 804, 830 and 801 days, respectively. The design of the study also enabled an effect of parental age on lifespan of female progeny to be sought, but no effect was detected.