Using histamine provocation tests, bronchial responsiveness was measured in 43 children with atopic dermatitis, aged 7 to 15 years, who had attended pediatric dermatology clinics within the past 5 years. The children were divided into two groups, one group of 21 children in whom asthma had been previously diagnosed and in whom symptoms of asthma had occurred in the preceding year, and the other comprising 22 children who denied any such symptoms. Bronchial hyperresponsiveness (as defined by a 20% fall in forced expiratory volume in 1 second at a provoking dose of histamine of 7.8 mumol or less [PD20]) was demonstrated in all but 1 of the children with atopic dermatitis and asthma, in 18 of the 22 children with atopic dermatitis alone, but in only 3 of a control group of 18 children without atopic dermatitis or asthma. The asthmatic subjects (median PD20 = 0.22 mumol) had more severe bronchial hyperresponsiveness than the nonasthmatic subjects (median PD20 = 2.10 mumol). This study confirms the strong association between atopic dermatitis and bronchial hyperresponsiveness, even in the absence of overt asthmatic symptoms.