Ageing is associated with greater susceptibility to nutritional deficiencies and to progressive senescence of the immune system. Ascorbic acid has been reported to have a corrective influence on the alteration of immunological functions that occurs during ageing. We examined the effect of a daily oral dose of ascorbic acid (20mg/100g body weight for 15, 30, and 60 days) on immune responses in young and old rats. A significant increase was observed in the total leucocyte count in both young and old rats after 60 days of ascorbic acid supplementation. When rats were fed the normal diet, the values of phagocytosis, nitroblue tetrazolium reduction test, and soluble immune complex were lower in the older animals than in the younger. On supplementation with ascorbic acid, an increase in all these immunological functions was observed, the increment being highly significant in old rats after 60 days of ascorbic acid supplementation. Hence, our results suggest that dietary intake of ascorbic acid influences the cell-mediated immunity during the ageing process.