Seeds of Canavalia maritima are ground after removal of the external coat and are used for the construction of a new enzymatic electrode for urea. Aliquots (10 mg of the powder) are immobilized at the surface of an ammonia gas-sensing electrode, via glutaraldehyde or, alternatively, on PVC membranes. The analytical performance of the biosensors for serum urea determination is comparable to the spectrophotometric method.67593596