Investigation of the thrombocytopoetic functions of the bone marrow was performed on the clinical tissue culture of the bone marrow in the patients with silicosis to observe number and motor activity of the megakryocytes. 1) No definite differences of the number and motor ability of the megakryocytes were observed between the normal persons and silicosis patients. 2) Definite differences of the hematopotic functions in according with defferent types of the disease which were noted in the erythropoetic and leucopoetic system were not demonstrated in the thrombocytopoetic system. 3) Above findings are reasonable to presume that several factors affecting silicotic changes or secondary pathological changes following silicosis are not influenced to the thrombocytopoetic functions.