Studies on rosette-forming cells and IgG, IgA, IgM and IgE-bearing lymphocytes were carried out in 70 healthy children aged 5 to 15 years. Furthermore, in 20 of these children, the percentages of IgG, IgA, IgM and IgE-containing blast cells after pokeweed mitogen stimulation of peripheral lymphocytes were evaluated. No differences in the percentages of rosette-forming cells, or in Ig-bearing and Ig-containing cells were found when three different age-groups were compared.