1. Seven more diabetic dogs have been implanted with complete feedback artificial beta cell systems. 2. All of these units have functioned fairly well with maintenance of the animals in the process of extensive surgery but none have brought the animals under complete control. 3. The glucose sensors are at fault because they are insensitive to the glucose levels giving readings that appear functionally to be about half of true readings. 4. The defective function of the electrodes has been traced to the design of the electrodes which does not take the Km of glucose oxidase for oxygen into consideration. 5. Redesign of the electrodes by inclusion of a convertor for pO2 based on the reading of the reference electrodes leads to a reliable glucose reading. 6. It is recommended that all glucose electrodes which are based on glucose oxidase be redesigned to include an oxygen electrode to permit correction of the readings to account for the effect of local pO2 on their function.