The children of early age with thymomegalia and acute obstructive bronchitis suffer from lower T-lymphopoiesis in thymus gland evaluated on content of T-receptor excision rings. The T-receptor excision rings represent ring-shaped DNA molecules detecting only in T-cells recently emigrated from thymus gland. They serve as a measure of intensity of maturation of T-lymphocytes and their migration from this gland i.e. functional activity of this organ. The addition of immune modulating preparation tactivin to the complex treatment of acute obstructive bronchitis promotes repairing of affected T-lymphopoiesis. Besides, content of T-receptor excision rings practically reaches the level detected in children without thymomegalia.