Similar frequencies of atopic diseases and of elevated total serum IgE levels were observed in 40 children with serum IgA levels below 5 mg/dl and absence of salivary IgA (severe selective IgA deficiency, SIgAD) and in 40 children with serum IgA levels above 5 mg/dl but below -2 SD of age-normal mean values and presence of salivary IgA (partial SIgAD). These findings suggest that the absence of secretory IgA, which has been postulated to play a protective role by excluding allergens at the mucosal level, does not appear to play a crucial role in the pathogenesis of atopic diseases.