The adsorption of urease onto a well-defined solid support, petroleum-based activated charcoal, has been achieved to provide the enzymatic hydrolysis of urea. In order to produce a biocompatible surface, the enzyme support system has been coated with hexamethyldisiloxane through plasma polymerization. The quality of the resulting coat was tested by electronic spectroscopy for chemical analysis and scanning electron microscopy techniques. Studies on the adsorption of urease, and activity and stability of the enzyme on the support have been in the direction to optimize the features of the charcoal-supported urease and improve its availability for further use in clinical applications. (C) 1996 Elsevier Science Limited.