BACKGROUND: OBJECTIVE: METHODS: RESULTS: Sufficiently complete data were available for 403 children. Eczema within the first 2 years of life was clearly associated with an increased risk of childhood asthma in boys (adjusted odds ratio, 2.45; 95% CI, 1.31-4.46) but not in girls (odds ratio, 0.88; 95% CI, 0.43-1.77; P for interaction = .031) even with adjustment for the effects of early allergic sensitization and wheeze. If these relationships are causal, an intervention to prevent eczema in boys might reduce the incidence of childhood asthma by as much as 28%. CONCLUSION