Ageing induces a change in immune responses. Besides this, impaired nutritional status is considered to have a critical influence on immune function, which may be reversed by nutritional supplementation. We evaluated the effect of an enriched drink on immune function in the elderly. 33 frail elderly subjects (aged > or = 65 years and body mass index < or = 25) received two 125 ml packages of either an enriched drink (n=20) or placebo (n=13) daily for 6 months. The enriched drink contained macro- and micronutrients. At baseline and after 6 months blood samples were drawn and PBMC's were isolated. ConA stimulated proliferation and IL-2 production of PBMC's were measured. There was a significant difference between groups in proliferation over the study period. The supplement group remained stable whereas the placebo group showed a reduction in proliferation over the 6-month period. There was no significant difference in IL-2 production between groups. Our study adds to the evidence that nutritional supplementation can affect immune function in the elderly.