Absorption of lactulose and mannitol was measured in eleven patients with atopic eczema and lactulose/mannitol excretion ratios were calculated. Mean lactulose absorption was increased in the patients with exzema and their excretion ratios were higher than those of controls. There was no correlation between either eczema extent or severity and the excretion ratio. We conclude that small intestinal passive permeability is increased in some patients with atopic eczema.