Glucose-oxidase-based sensors were realized using three techniques of immobilizing thin layers of enzyme over a three-thin-film electrode transducer. Sensors with chemically crosslinked membranes, completed by an outer diffusion-limiting membrane, were characterized with consideration of the basic requirements of an implantable device. Thus, e.g. a negligible loss of the activity was observed when the sensors were sterilized by a 2.5 MRad dose of gamma radiation. On the other hand, the sensors with the electrochemically deposited membranes were particularly suitable, e.g. with respect to response time, etc., for flow-injection analysis measurements.