Investigations are reported on the gas source iodine doping of CdTe grown by molecular‐beam epitaxy, utilizing ethyliodide as the dopant precursor. Structural and electrical characterizations of these layers showed them to have favorable crystalline properties and indicated that the electrical activity of iodine in CdTe was between 50% and 100%. Electron concentrations between 6×1016and 3×1018cm−3were obtained and showed the highest mobilities measured in epitaxialn‐type CdTe. These studies also showed that the incorporation of iodine was independent of the II/VI flux ratio and that its electrical activity was independent of both dopant concentration and II/VI flux ratio. The photoluminescence spectrum at 10 K was dominated by strong excitonic recombination bound to ionized and neutral iodine donors. These results demonstrate that iodine is a highly effective donor in CdTe.