||OBJECTIVES: To describe the development of atopic dermatitis (AD) during the first 3 years of life and identify the localization of the early skin lesions that predicts the development of AD. DESIGN: Prospective, longitudinal, birth cohort study of children born to mothers with a history of asthma, followed up for 3 years with scheduled visits every 6 months as well as visits for onset or acute exacerbations of skin symptoms. SETTING: The cohort was recruited from greater Copenhagen, Denmark, and followed up at a clinical research unit, which controlled all diagnoses and treatment of skin diseases. PARTICIPANTS: A total of 411 infants were enrolled in the cohort; 55 had incomplete follow-up and were excluded from certain analyses. MAIN OUTCOME MEASURES: Atopic dermatitis was defined based on the criteria of Hanifin and Rajka, and severity was assessed by the SCORAD (Scoring Atopic Dermatitis) index. Predictive odds ratios of early skin lesions for those who developed AD vs those who did not were calculated. RESULTS: The cumulative incidence of AD by age 3 years was 44% (155/356). The prevalence rate peaked at age 2 years for boys and at age 2.5 years for girls, but there were no other sex differences in the proportion of children developing AD. Skin involvement in infants with AD was found to begin at the scalp, forehead, ear, and neck in a balaclava-like pattern and continue to the extensor sides and trunk, finally affecting the flexor sides of the extremities. Early skin lesions of arms and joints best predicted AD at age 3 years. CONCLUSIONS: Atopic dermatitis begins at the scalp, forehead, ear, and neck in a balaclava-like pattern. Eczema at the arms and joints provides the highest predictive value for the development of AD at age 3 years. This may be used for early prediction and intervention of AD.