Previously we reported¹⁾ that the oily concentrate containing sarkomycin free acid (Sy), purified by the solvent extraction method from the cultured broth, reacts with isonicotinic acid hydrazide (INAH) to form biologicaly active and low toxic solid substance (SI) under some conditions. This substance was stable in antibacterial activity in short period of storage. In the present paper, we report the optimum condition for its preparation and its stabilities in long period of storage under various conditions not only in antibacterial activities but also in antitumor activities. Materials, bioassays and animal tests are the same as reported in the previous paper¹⁾.