Primary pulmonary cryptococcosis is thought to be relatively less common than other lung mycoses, but recently there has been an increase in reports of patients with this disease. Our report covers 12 cases of primary pulmonary cryptococcosis in which the diagnosis was based on medical examinations. The patients consisted of 11 men and 1 woman, aged 27 to 58 years. Only 3 exhibited subjective symptoms. Roentgenograms showed cavitating tumor shadows in the lungs of 2 of the patients with subjective symptoms, and nodular shadows with diameters of 1.0 to 2.8 cm in all patients without subjective symptoms, indicating the possibility of lung cancer. The disease was diagnosed in 3 patients on the basis of transbronchial biopsy findings, and in 9 on the basis of needle aspiration biopsy findings. One patient was diabetic, but the others did not exhibit malignancies or other immunocompromised states. Antifungal drugs significantly reduced or eliminated the nodular shadows in 10 patients. Because patients with primary pulmonary cryptococcosis frequently lack subjective symptoms, prompt diagnosis is critical, particularly in view of the need to distinguish the disease from lung cancer.