Changes in the oral microbial flora, some of which are related to mucosal disease, have been detected in the elderly, but the causes are not fully understood. This study has examined the possible role of micronutrient depletions in the reduced colonisation resistance and oral infection exhibited by some elderly subjects. The oral health, oral microbiology and micronutrient status of 37 geriatric patients aged 65-91 years (mean 81 years) were examined. Ten of the patients had no oral mucosal disease. Mucosal pathology in the remainder included erythema (27%), denture stomatitis (24%), angular cheilitis (16%) and atrophic glossitis (41%). Those with mucosal pathology had significantly lower serum iron concentrations (P = 0.02). Serum or plasma concentrations of zinc, copper, selenium, C-reactive protein, transferrin, caeruloplasmin, albumin, vitamin A and vitamin E were not significantly different between those with oral disease and those with healthy mouths. Similarly, activity of the selenium-containing enzyme, red cell glutathione peroxidase, did not differ significantly between the two groups. In both groups, plasma selenium concentrations (82%), red cell glutathione peroxidase activity (47%), plasma zinc concentrations (58%) and albumin concentrations (44%) tended to be below the lower limit of the reference interval. The influence of subclinical infection on these values is discussed.