Antibody‐dependent monocyte‐mediated cytotoxicity was investigated in adult patients with atopic dermatitis. In patients with active dermatitis monocyte cytotoxicity was reduced. Serial studies of individual patients demonstrated that a reduced cytotoxicity in clinical exacerbation did not normalize during clinical remission. The reduced monocyte cytotoxicity was not caused by an abnormal influence of lymphocytes. During the cytotoxicity reaction a rapid and transient elevation of monocyte cyclic AMP occurred. In atopic dermatitis this elevation was decreased, but no relation was found between the monocyte cytotoxicity and the cyclic AMP response in these patie