1. Aspirated sternal bone marrow was studied in 9 patients with active brucellosis. Eight of the 9 patients had a demonstrable bacteremia due to Br. abortus.
2. Particles of marrow in 4 of the 9 patients revealed the presence of granulomatous lesions. In 1 case, the presence of a relatively large lesion permitted the study of the lesion in detail by means of serial sections. The alterations in the cellular pattern of the marrow and of the peripheral blood of the 9 patients were described.
3. The histopathology of the marrow in active brucellosis has been compared with the alterations in the other organs and tissues as reported in the literature. Comparisons have also been made between the granulomatous lesions in the marrow of brucellosis and those found in tuberculosis and sarcoidosis.
4. Aspirated sternal marrow for cultural and histological purposes merits further consideration as a diagnostic aid in active brucellosis.