The luminescence of single crystals of wurtizite CdS having a strong green‐edge emission was studied at 4.2° and 77°K as a function of exciting intensity of steady 3650‐A˚ light. The typical overlapping band structure of the green‐edge emission, a zero phonon band with ∼300 cm−1phonon replica bands, was seen to shift to longer wavelengths with decreasing intensity of the exciting light. This behavior, seen in the green edge of GaP, suggests that the green edge arises from the recombination of electrons and holes trapped on distant donor and acceptor pairs.