"Releasability" is the theory whereby biochemical events in basophils influence the capacity to release chemical mediators in response to activating stimuli. We have compared the releasability of basophils from 21 young patients with atopic dermatitis (AD) with that from 17 normal donors of matched ages. Basophils were challenged with several different stimuli: rabbit antihuman Fc epsilon (anti-IgE), N-formyl-methionyl-leucyl-phenylalanine (f-met-peptide), Ca++ ionophore A23187, and D2O. Basophils from patients with AD released significantly more histamine both "spontaneously" and in response to D2O than did controls. The basophils of patients with AD were significantly more responsive to anti-IgE and to A23187. There was no difference between the percent f-met-peptide-induced histamine release in patients with AD vs controls. No significant correlation between percent histamine release with optimal or suboptimal concentrations of the stimuli and serum IgE level was found. There was a significant correlation between the sensitivity of the cells to release with f-met-peptide and the response to A23187 both in control and in AD patients. Since basophils are thought to play some role at the site of inflammation in AD, their increased releasability might contribute to the symptoms of these patients.