Monocytopoiesis and blood monocytes were investigated in nine patients with active tuberculosis and in six patients with active sarcoidosis in order to obtain information on monocyte consumption in these two types of granuloma. All patients with tuberculosis demonstrated a marked increase in proliferation activity of monocytopoiesis and premature monocyte marrow release. These changes indicate a high monocyte consumption which probably is caused by a high macrophage death rate due to the high macrophage-toxicity of tubercle bacilli. Thus, tuberculous lesions are an example of a "high turnover granuloma". In sarcoidosis monocytopoiesis showed no significant deviations from the normal. This indicates a low macrophage turnover or "low turnover granuloma". Thus, any hypothetical agent assumed to be involved in the pathogenesis of sarcoidosis would have to possess low macrophage-toxicity.