The effect on cellular immunity of the administration of the non-specific immunopotentiator BCG and/or a streptococcal agent was studied in 90 non-cancer bearing Wistar rats under different nutritional support. The number of immunocompetent cells and the non-specific function of the immunocompetent cells significantly decreased in acute malnutrition. The non-specific immunopotentiator BCG and streptococcal agent activated the peritoneal macrophages, to a remarkable extent, but depressed spleen cell blastoid transformation, thymus index and peripheral lymphocyte count in the starved rat group. In rats who received BCG under intravenous hyperalimentation (IVH), the absolute macrophage counts went down as the quantity of amino-acid administered decreased. The acquired immunodeficiency due to acute malnutrition is evident and the effect obtained with an immunopotentiator is considered to be related to the nutritional status of the host. The adequate administration of protein-calorie is required for the effective use of the immunopotentiator.