A series of compounds are described which exhibit therapeutic activity in experimental tuberculosis, acting exclusively on the host. The active compounds (citronellyl acetate, d-limonen, linalyl acetate) induce a local India ink and trypan blue accumulation and also stimulate the macrophages in vitro and in vivo to an increased phagocytic activity. Sera of the animals treated with therapeutically active compounds stimulate the macrophages of normal animals to an increased phagocytosis. A correlation between chemical structure of the reticulo-endothelial system stimulating compounds and the above effects is discussed.