We report the results of time-resolved studies on the exciton radiative decay in single-crystal GaN films grown by metalorganic chemical vapor deposition. Time-resolved photoluminescence (PL) measurements were performed on the samples at various temperatures from 10 to 320 K. The well-resolved near-band-edge luminescence features associated with free excitons and bound excitons in the GaN allow us to unambiguously determine their decay times. We found that the nonradiative recombination processes play an important role and dominate the decay of exciton population. The processes depend on the density of defects and impurities in the GaN samples.