The electron time decay in an afterglow following a short pulsed d.c. discharge in CO has been investigated using microwave diagnostic techniques. The gas was heated to an average temperature of 775 OK. Two-body electron-ion recombination and ambipolar diffusion were found to be the only important electron removal mechanisms present in the pressure interval 0.2 < p < 2 Torr with the rate constants a, = 3.9 x cm3 s-I and D,po = 372 cmZ s-I Torr respectively. If we postulate a T-Y dependence for a,, comparison with room temperature results yields y = 0.57. The diffusion coefficient appears to increase strongly with temperature based upon an estimated zero field mobility for CO+in CO at 273 "K found in the literature.