Five hundred and thirty families with at least 1 child who had been referred to a dermatologist with atopic dermatitis were interviewed in an effort to determine whether factors such as the age of the mother when a child is born and/or birth rank can contribute to the development of atopic dermatitis. The families interviewed had a total of 1,084 children, or an average of 2 children per family. Sixty per cent of the children with atopic dermatitis were under 5 years of age. Ninety-one per cent of them had developed the disease before the age of 3; those most severely affected had developed the disease during the first year of life. In families with 2 children, but only 1 child with atopic dermatitis, the odds ratio for the second child to develop atopic dermatitis was 1.379 (0.025 < p < 0.05). The average maternal age was 24.8 to 25.2 years when giving birth to the first child and 28 years when giving birth to the second child, irrespective of the status of the child. Thus, atopic dermatitis can be related to birth rank or to the age of the mother.