The kinetic characteristics of an invertase immobilized covalently on porous silica have been appraised for the applicability of porous silica to immobilization supports of enzymes. The invertase was covalently bound with glutaraldehyde on 3-aminopropyltriethoxy-silane-activated porous silica to give a maximum loading of 120mg invertase per 1 gram of dry silica and 26.9 to 70.2% retention of original activity. The porous structure of silica seems to be suitable for enzyme immobilization, judging from the observed results of high immobilization capacity and comparably satisfactory retention of enzyme activity.