With the purpose of studying the influences of sulfonamides on the leucopoietic function of bone marrow, the bone marrow tissue culture (cover-slip method) of the rabbit was conducted. Sulfonamides were added to the tissue culture medium at various concentrations, and the effects of these drugs on the tissue growth were observed; and the following results were obtained. 1. Sulfonamides such as sulfanilamide, sulfapyridine, sulfathiazole, sulfisoxazole, sulfisomidine and carbutamide, at the concentration equivalent to the therapeutic blood level (1-20mg/dl), exerted no appreciable effect on the tissue growth of bone marrow. 2. These sulfonamides showed slight inhibitory action on the tissue growth of bone marrow at the higher concentration than 20 mg/dl.