PVC membrane electrodes that are selective and sensitive to copper(II) have been developed. The best electrode, based on 13,14-benzo-1,5-tetrathiacyclopentadecane and 2-nitrophenyl octyl ether solvent mediator with a potassium tetrakis(p-chlorophenyl)borate anion excluder, exhibits a linear response in the range 10–1–10–6 M over the pH range 2.9–6.7 and has a Nernstian slope of 28–29 mV per decade at 25 °C. The response time is 10 s.