A special questionnaire was developed to obtain up-to-date data on the prevalence of atopic dermatitis among children. It was validated by specialist diagnosis in 320 children, providing a diagnostic sensitivity and specificity of 97%. This questionnaire was used for all school entrants in 1990 in the Hanover District. A total of 4,916 children were examined and the questionnaire satisfactorily completed by a relative or guardian (usually the mother) of 4,651. The prevalence of atopic dermatitis was 11.8%, ranging from 8.4% to 17.3% among the 20 constituent communities. The regional differences were smaller than the scatter of diagnostic classifications by the school doctors and the reports of a positive history by the parents. The results demonstrate the validity of a systematic enquiry employing relevant diagnostic and anamnestic items.