To describe the distribution of serum total IgE and specific IgE to common aeroallergens by sex and age and to study their relationship to each other, we measured serum total IgE and specific IgE (CAP) to house-dust mite, timothy grass, cat, birch, and Cladosporium in a random sample of 2496 subjects, aged 20-70 years from the Dutch general population. We found that total IgE was higher in men, independently of smoking, and that total IgE had no relationship with age after adjustment for specific IgE and smoking in linear regression analysis. At least one positive specific IgE test was found in 32% in both sexes. Men had higher prevalences of specific IgE to house-dust mite and lower prevalences of specific IgE to birch than women. The proportion with positive specific IgE decreased with age. The mean total IgE increased with the number of positive specific IgE tests. Thus, total IgE is higher in men and has no relationship with age if specific IgE is taken into account. The prevalences of specific IgE to aeroallergens are high and decrease with increasing age. We suggest that sex differences in total IgE should be considered when using total IgE.