In a normal population aged over 70 years the geometric mean IgE value of 30.6 u/ml was not significantly different from that obtained previously in a similar epidemiological survey of a population aged 20-44 years. However, in the older population we have noted a significant sex difference-38.6 u/ml for males against 27.2 u/ml for females-which was only apparent in the atopic subjects of the younger population. There have been some other reports that IgE levels decrease with age, and possible reasons for these differences with our own results are discussed.