Alternating cyclic, A.C., selective area epitaxial growth of silicon on thermal oxide masked, ion‐implanted substrates was studied in a hot wall, low pressure epitaxial system. Ion‐implanted surfaces are notoriously bad insofar as obtaining selective growth is concerned. Using the Si‐H‐Cl‐Ar system, the A.C. process employs an embedded disproportionation chemistry within the overall deposition process, which provides an effective mechanism for the prevention of the formation of spurious nuclei on dielectric masks. The disproportionation chemistry is made dominant cyclically, by pulsing the hydrogen off and on periodically during the deposition process, while maintaining the flow of the reducible source gas, , in order to prevent the formation of incipient nuclei. Experiments were conducted at 2.5 Torr, 950°C, , , with , , and , which were found in an earlier study to represent worst case conditions in terms of spurious nucleation. It was found that the heavier ion‐implantation dose, as well as increased deposition thickness, enhanced dramatically the tendency for spurious nucleation to occur on the masked regions. However, in all instances, the A.C. technique was found capable of preventing the formation of spurious nuclei on masked areas, guaranteeing essentially 100% selectivity control, even for epitaxial films as thick as 2.4 μm (which were the thickest grown).