Fifty-seven subjects, forty-three with various combinations of atopic disease and fourteen non-atopic controls, were studied using a battery of immediate skin test allergens and a radio-immunoassay for serum Immunoglobulin-E (IgE). The geometric mean serum IgE level (units/ml) was 50 in strictly nonatopic controls, 170 in atopic respiratory disease (ARD) patients, 320 in atopic dermatitis (AD) patients and 772 in those patients with both AD-ARD. The marked elevation of the serum IgE in the latter group was not associated with respiratory disease activity and not closely correlated with extent of the dermatitis, but may relate to patients with both AD-ARD being 'highly atopic'. Overall, there was no correlation between the serum IgE level and the frequency of positive skin tests. Compared to ARD patients, the serum of AD patients contained more IgE, yet they reacted significantly less frequently to common extrinsic allergens.