The dehydrogenation of highly photoconductive amorphous silicon films has been studied using15N,pnuclear reaction hydrogen depth profiling and isochronal anneals at temperatures between 300 and 500 °C. The studies shown that neither diffusion nor a first‐order reaction are the rate limiting dehydrogenation mechanism for hydrogen concentrations between 5 and 40 at. %. Dehydrogenation is not rate limited by processes at the surface. The studies suggest that for concentrations above 5 at. % the dehydrogenation may be explained by second‐order reaction kinetics involving the reordering of bonds. Below about 5 at. % a first‐order process leading to dangling silicon bonds appears to dominate.