IgE levels were measured in serum and various external secretions from normals and patients with respiratory, intestinal, gynecological and dermatologic diseases. No IgE was detected in cervicovaginal secretions. The small intestinal secretions also had no detectable IgE, but did have a substance that inhibited the precipitation of IgE – anti-IgE, and was possibly a degradation product of IgE. The IgE:IgG ratio in sputum, nasal washings and saliva was greater than that of serum, suggesting that IgE is a secretory immunoglobulin. IgE levels were highest in these secretions and in serum of patients with extrinsic asthma and neurodermatitis.