In a subgroup of patients with atopic eczema (AE), eczematous skin lesions can be induced by epicutaneous testing with aeroallergens (the atopy patch test: APT). An increased frequency of positive APT has been found in AE patients showing a predictive lesional pattern affecting air-exposed skin areas. This study investigates the dose-response of the APT in two different patient groups with AE. Petrolatum preparations of house dust mite, cat dander and grass pollen allergens in four concentrations (500-10,000 protein nitrogen units) were tested epicutaneously in 57 patients with AE, who were prospectively divided in two groups according to whether their AE pattern was with (group I) or without (group II) a predictive distribution. Sixty-nine per cent of patients in group I, and 39% in group II, had positive APT reactions (P = 0.02). The reactions in group I were elicitable with lower allergen concentrations (P = 0.03). A clinically recognizable subgroup of patients with AE showed increased cutaneous sensitivity to aeroallergens.