The aim of the study was to establish diagnostic criteria for atopic dermatitis in 1.5-year-old children that could be employed in epidemiological studies of atopic dermatitis based on telephone interviews. In a Danish cohort of 100,000 pregnant women, 4 computer-assisted telephone interviews were carried out. In the last interview, conducted when the child was 1.5 years old, mothers were asked about their child's skin condition. Eighty-one women who had answered that their child suffered from either an itchy rash or atopic dermatitis were invited to participate in the study. Of these, 60 took part in the study and had their child examined by a dermatologist. Affirmative answers to 1) itchy rash or doctor-verified atopic dermatitis and 2) recurrent rash or rash for at least 4 consecutive 0.5-month periods, and 3) localization in elbow creases, behind the knees, wrists/hands, face or generalized rash resulted in the highest sensitivity and specificity for atopic dermatitis as diagnosed by the dermatologist, who found 37 of 60 children (62%) suffering from atopic dermatitis. Using this algorithm, telephone interviews can be used to diagnose atopic dermatitis in young children in large-scale epidemiological investigations.