Previously we reported on the lymphocyte-stimulating activity of the hypocalcemic substances (TP1, TP2) which were isolated from the bovine thymic extracts, and on their possibility of promoting immune competence (A. Mizutani, et al., Ann. N. Y. Acad. Sci., 249, 220 (1975)). To acquire the direct evidence for promoting immune competence, both substances and several fractions, which were obtained from the thymic extracts in the course of purification, were examined for the increase in antibody-producing cells (PFC activity) in mice by the Jerne method with a minor change. Roughly, it was recognized that there was a tendency for the promotion of PFC activity of the fractions to be dependent on that of their hypocalcemic activity accompanied by lymphocyte-stimulating activity. In the administration of both TP1 and TP2, in a dose of 1 μg/mouse, to neonatal mice, significant PFC activity was found. Thus it gives a clearer understanding of the action of promoting immune competence taking the lymphocyte-stimulating action into account.