Impaired beta-adrenergic and enhanced alpha-adrenergic reactivity have been implicated in the pathogenesis of atopic dermatitis. We have measured the elevation of cyclic AMP in peripheral blood leukocytes in response to isoprenaline, histamine and prostaglandin E2, in the presence and absence of a phosphodiesterase inhibitor. An impaired response to beta-adrenergic stimulation was demonstrated in subjects with atopic dermatitis but impaired responses were also observed with histamine and prostaglandin E2. In vivo, both noradrenaline and salbutamol caused significant inhibition of the histamine-induced weal response in atopic and normal subjects. However, there was no significant difference between the two groups when alpha- and beta-adrenoceptor responses were compared.