It is shown that the blue luminescence band appearing at room temperature in ZnSe is seen in metalorganic chemical vapor deposition (MOCVD) epilayers with carrier concentration 1×1018 cm−3. The photon energy at the emission peak is the same in this material as in material with much lower carrier concentration. Properties of the blue band are surveyed to discriminate between different possible assignments. It is concluded that Shirakawa and Kukimoto [J. Appl. Phys. 51, 2014 (1980)] were correct in assigning it to a transition between a free hole and an electron bound to a donor. However, not all donors contribute. There is a cutoff energy within the spread of donor levels above which there is negligible contribution to the emission. It is suggested that the cutoff corresponds to a localization edge of the same nature as the mobility edge.