The authors examined 536 children 10 years of age to evaluate their immune status and the development of allergies and recurrent respiratory inflammations. Altered resistance was found in as many as 47% of children, pollen allergy and atopic eczema in at least 10.5%, habitual rhinitis in 15.2%, asthma in 3.5% and recurrent inflammatory infections in 13.1%. A higher rate of alterations was found where environmental conditions were deteriorated. Elevated IgE, changes in IgG, IgA and IgM as well as increased levels of acute phase proteins suggest a relationship between the degree of immune impairment and clinical manifestations. Our results imply there are large numbers of children with altered immunity and point to the fact that in common practice only 14% of them are attended to by the clinical immunologist and thus receive causal treatment. It is therefore concluded that, in line with the expansion of noxious factors which accompany our civilization, more attention should be given to the development of immunity in the young population.