Clinically healthy subjects of the Indian population were divided into three age groups: young, 8-14 years; adult, 20-35 years; old, > or = 55 years and were further classified based on body mass index (BMI) as normal BMI (NBMI)> or =20 and low BMI (LBMI) between 16 and 18, respectively. The ability of the peripheral blood lymphocytes from these subjects to respond to PHA stimulation in vitro and DNA-repair parameters, thereafter as a function of BMI and aging, were studied. The DNA-repair markers like unscheduled DNA synthesis (UDS), activities of DNA polymerase beta and of two endodeoxy-ribonucleases, (UV- and AP-DNases) were assessed under different conditions. The LBMI group, considered to be going through chronic but mild undernutrition, showed higher repair capacity and exhibited no appreciable age-dependent decline in DNA-repair potential as was seen in normal subjects. These results correlate well with those seen in unstimulated human lymphocytes and also confirm the observations made earlier in experimental animals, where dietary restriction was shown to have beneficial effects on DNA-repair capacity.