By means of clinical bone marrow tissue culture influences of sympathetic stimulating or blocking drugs and parasympathetic stimulating or blocking drugs on the function of megakaryocytes were observed. The solution of these drugs at various concentrations were added directly to the culture media and obtained the following results: 1) The function of megakaryoctes was diminished when epirenamine or nor-epirenamine being sympathetic stimulating drugs added to culture media. 2) 2-Benzyl-imidazoline-hydrochloride being sympathetic blocking drugs accelerated the function of megakaryocytes. 3) In the cases administered acetylcholine hydrochloride or bethanechol chloride which are parasympathetic stimulating drugs the function of megakaryocytes were accelerated. 4) No effects on the function of megakaryocytes were observed when atropine sulfate or dl-tropyltropate-n-methylbromide were added to culture media directly. These results may conclude that the function of megakaryocytes are diminished when adrenaline that is produced at the end of sympathetic nerve affects on bone marrow directly and also the function of it is accelerated when acetylcholine which is produced at the end of parasympathetic nerve affects on bone marrow directly.