An extracellular endoinulinase P-III from Aspergillus niger 12 has been immobilized covalently onto bromoacetyl-cellulose (BAC), cellulose-carbonate (CC) and CNBr-activated Sepharose 4B (CAS) with the activity yields of 1 1.9, 24.1 and 19.3 % , respectively, under optimal reaction conditions for the immobilization. All three immobilized enzymes increased the resistance to inactivation by p-chloromercuribenzoate or Fe3'. Mn2. stimulated the activities of the immobilized endoinulinases onto CC (160 %) and CAS (168 %) more remarkably than those of free and BACimmobilized enzymes (124 %). The marked rise from 45 to 60'C in the optimal temperature for inulin hydrolysis was observed in the CAS-immobilized enzyme. The pH stability decreased on the acidic side and increased slightly on the alkaline side in the BAC-inunobilized enzyme, and shifted to the acidic side in the CC-immobilized enzyme. The K~ value decreased in the BAC-immobilized enzyme and increased in the CAS-immobilized enzyme.