THE ROENTGENOGRAPHIC appearance of discrete miliary opacities or diffusely distributed pulmonary lesions often presents a difficult diagnostic problem. The differential diagnosis includes miliary tuberculosis, sarcoidosis, fungus disease, metastatic carcinoma, pneumoconiosis, and pulmonary fibrosis, as well as many less common diseases.1 Diffuse involvement of the pulmonary parenchyma sufficient to produce a miliary-nodule appearance roentgenographically is frequently associated with disseminated disease. When the diagnosis cannot be established on the basis of bacteriologic, mycologic, or immunologic findings, biopsy of tissue involved by the disease process is desirable. In the absence of enlarged lymph nodes, biopsy of the lung, liver, or marrow may be necessary in order to establish a diagnosis. Lung biopsy is a comparatively radical procedure, whereas needle biopsy of the liver or examination of the marrow is easily performed and may furnish valuable information. In order to investigate this problem, the sternal marrow was studied in 24 patients with diffusely