The contribution of the PQ and PQ levels to the secondary ionization coefficient in a Townsend discharge are discussed. In the case of a research grade krypton gas sample, the theoretical values of 8 / a (the dominant process in the range E/p < 50 volt cm1 torr1 ) are in good agreement with the experimental values of co / a . However, in the case of purified research grade krypton gas samples, it seems likely that only atoms in the PQ level contributed to the secondary ionazation coefficient