Light absorption techniques are used to study the temporal dependence of the number densities of the 5s′00 and 5s12 krypton metastable atoms during the decay period (afterglow) of a pulsed discharge in krypton and krypton–nitrogen mixtures. The sensitivity of the temporal properties of the 5s′00 state of krypton to discharge pulse conditions was attributed to an electron destruction process. The 5s12 state was not affected by discharge excitation conditions, permitting the measurement of the diffusion coefficient (Dp0=29.3 cm2 sec−1 Torr) and of the two-body and three-body reaction rate constants in pure krypton (k1=2.44×10−15 cm3 sec−1 and k2=2.59×10−32 cm6 sec−1, respectively). In krypton–nitrogen mixtures the additional loss of the 5s12 state of krypton due to its reaction with nitrogen was determined to have a reaction rate constant of 3.33×10−12 cm3 sec−1. Light emission studies made using a flowing afterglow system show that this process populated a wide range of vibrational levels of the B 3Πg state of the nitrogen molecule.