Total IgE levels in sera of 165 patients with atopic dermatitis and 79 patients with dermatoses as well as normal control patients were determined by radioimmunoassay (Phadebas, Pharmacia). Although the mean value for patients with atopic dermatitis was found far above the mean value for normal controls, 38% of patients showed total IgE serum levels within the normal range. Highest IgE serum levels were observed in patients with the generalized form of the disease and in patients with asthma and allergic rhinitis. No direct correlation however, to severity of disease could be found. In a series of 50 patients prick tests were compared to total IgE serum levels and to levels of allergen specific antibodies determined by radioallergosorbent-test (RAST). Extracts of grass pollens and of animal dandruff were used. There was complete agreement between results of skin testing and RAST in at least 80%. While cross reactions were common with grass pollen extracts in RAST, there was no cross-over with animal dandruff. No correlation was found between titer of allergen specific antibody and severity of skin lesions. IgE specific antibody could be detected in 48% of patients with normal total IgE serum levels and in 82% of patients with elevated values.