Rat bones demineralized in HCl and TCA exhibited distinct osteoinductive activity while the bones demineralized using EDTA did not show the activity. HCl- and TCA-extracts of bones differed from EDTA extracts by chromatographic and radiochromatographic profiles. At the same time, HCl- and TCA-extracts contained additional fraction. The substances involved in the fraction appear to be responsible for inhibition of the osteoinductive factor of bone tissue.