Incidence of atypical mononuclear cells in the peripheral blood of children.

The presence of atypical mononuclear cells in the peripheral blood is a regular feature in all age groups examined, 1–3, 7 and 21 yrs. The frequency of these cells is highest in the youngest age groups, but only in one of the two investigation areas is this difference of statistical significance. The individual variation is great and the demarcation between normal and pathological is never well defined. Subclinical infections are probably of importance in this connection.