Serum samples from 60 adults and 64 children with atopic dermatitis were tested for antistaphylococcal IgE antibodies with RAST discs coupled to cellular proteins from Wood 46 strain S. aureus. Anti-S. aureus IgE antibodies were detected in 19 (29.6%) of the children and 14 (23.3%) of the adult patients. Anti-S. aureus IgE-positive adults had more severe and prolonged disease than those who were negative. Two groups of children comprising 10 who were anti-S. aureus IgE positive and 10 who were negative were compared. Children with anti-S. aureus IgE antibodies had more severe and more extensive disease (p less than 0.05), a greater prevalence of cutaneous S. aureus infections (p less than 0.05), higher mean total serum IgE level (p less than 0.05), a greater prevalence of specific IgE responses to food allergens (p less than 0.05), and a higher percentage of helper T cells (p less than 0.05) than children who were negative for these antibodies.