The spontaneous frequency of genetic damage and the possible relationship of this damage to dietary and nutritional variables were investigated in peripheral blood lymphocytes from 45 elderly people using sister chromatid exchange (SCE). The relationship of dietary and nutritional factors on SCE was assessed by different degrees of smoking status such as smokers (n=14), ex-smokers (n=16) and non-smokers (n=15). Significant relationship of the SCE frequency to nutrient intake of the combined subjects (n=45) was found. When cigarette smoking status was taken into account, there were negative linear relationships between SCE and fat, phosphorus or vitamin A intakes of the non-smokers as well as SCE and the dietary quality scores. There was a positive linear relationship between SCE and food frequency of meat and fish among the smokers. Use of artificial sweetners in ex-smokers of the elderly people produced a significant increase of SCE in comparison with the mean SCE for those not using sweetners. Other dietary parameters, including intake of coffee, green tea and ginseng tea, alcohol consumption, use of processed foods, and administration of vitamin pills did not show any correlation with SCE. These results suggested that dietary fat, phosphorus or vitamin A status are the major determinants of spontaneous DNA damage in lymphocytes of the elderly people.