Age-adjusted geometric mean IgE levels in 621 older subjects were higher in men (26.3 kU/L) than in women (19.1 kU/L), and decreased with age. The higher levels in men were largely a result of a strong positive association with cigarette smoking. Among allergic conditions, a personal history of asthma was associated with the highest IgE levels. In multiple linear regression models in men, cigarette smoking was the single strongest correlate of IgE levels, while a personal history of allergy was the strongest correlate in women. Our results suggest important nonallergic as well as allergic determinants of IgE levels in populations.