Pulmonary fungal infection has been investigated in patients with healed or active pulmonary tuberculosis or other lung diseases by demonstrating serum precipitating antibodies to the various fungal antigens and by isolating the related fungi from sputums or other clinical specimens. Out of 1,192 suspected patients, 405(34.0%) showed precipitin bands on immunodiffusion tests and the related fungi have been demonstrated in sputums or other specimens of 79.5% of them(327) whose specimens had been cultured. Three patients did not have precipitating antibodies to any fungal antigen, but the same fungus was repeatedly isolated from sputums of two patients for over one year of period and from open lung biopsy specimen in the other patient. Most commonly involved species in pulmonary infection were A. fumigatus(70.3%) and C. albicans (at least 23.8%), followed by A. flavus, P. boydii, A. nidulans, etc. Out of fungi isolated from individuals(459), who were apparently not infected with fungi, molds were 66.0% and the rest, yeasts. Most commonly encountered molds were aspergilli(31.7%), followed by penicilli(16.3%), Cladosporium spp.(2.8%), Fusarium spp.(2.2%), etc. C. albicans(16.6%) was of course most common yeast in human sputums and the other species were seen in few.