A thermostable inulinase was identified in a strain of A. niger. The highest activity was observed at 50 degrees C (50 Uml(-1)) and 77% and 34% of this was retained at 60 degrees and 65 degrees C, respectively. pH stability, the effect of thermal stabilizers such as Propylene glycol (10%) and Sorbitol (rob) and effects of different cations were investigated. It was found that the activity was completely inhibited by Ag+ and Hg2+ while Naf had an activator effect.