Serum neopterin levels were determined in 31 children and 18 adults with the selective IgA defici- ency and in 17 adult patients with a common variable immunodeficiency. The results were com- pared with serum neopterin levels of 41 children and 26 adult controls. All sera were obtained in an infection-free period. We observed significantly increased serum neopterin levels in common variable immunodeficiency patients; this increase was observed namely in patients with a severe course of the disease. No increase in serum neopterin levels was observed neither in IgA deficient patients prone to respiratory tract infections nor in IgA deficient persons examined for other rea- son (allergy, rheumatoid disease, etc.). The results stand against macrophage activation in the se- lective IgA deficiency.

        Key words: Neopterin - IgA deficiency - Common variable immunodeficiency - Antibody deficiency.