The oxygen dependence of oxidase enzyme electrodes is successfully addressed through the use of carbon paste biosensors with fluorocarbon pasting liquids. Due to the high oxygen solubility in perfluorocarbons, such pasting liquids provide an internal supply of oxygen, and efficient operation of first-generation oxidase electrodes under oxygen-deficit conditions. in particular, the use of poly(chlorotrifluorethylene) (Kel-F) oil results in an identical response up to 4 x 10(-2) M glucose, in the presence and absence of oxygen. Such oxygen independence compares favorably with that reported for mediator or wired enzyme electrodes. The internal supply of oxygen of a Kel-F/carbon paste enzyme microelectrode is not depleted over a prolonged operation under oxygen-deficient conditions. The oxygen effect upon the kinetic parameters of the immobilized enzyme is examined for a variety of pasting liquids. Such attention to the oxygen demand addresses numerous practical biosensor applications, involving low or fluctuated levels of oxygen, including in-vivo monitoring of glucose.