To investigate the role of Ca metabolism in granulomatous lung diseases, 187 patients with pulmonary tuberculosis 42 patients with sarcoidosis, and 47 patients with pneumonia were examined. The mean value of serum Ca on admission in tuberculosis patients was significantly lower than in patients with sarcoidosis. Of 183 patients with tuberculosis, 69 patients (38%) showed Ca level lower than normal range. The longitudinal observation of serum Ca level in 33 drug-responsive patients with tuberculosis disclosed that mean Ca level rose significantly at the third month of treatment, and maintained the similar level up to the sixth month. These findings suggest that the dynamics of Ca metabolism seen in tuberculosis were similar to that in pneumonia and differed from that in sarcoidosis, although both tuberculosis and sarcoidosis are characterized histologically by granuloma formation induced by cell-mediated immunity. To explain changes in Ca level, the chronological analysis of serum Vitamin D level was done, and it showed no correlation with serum Ca level. The lower serum Ca level on admission and their normalization according to the improvement of clinical course in tuberculosis have not been reported yet. It seems that there are responsible factors other than Vit D for Ca level fluctuation, and further studies are needed.