Electrical and photoelectric properties of glow‐discharged hydrogenated silicon films are measured as a function of hydrogen dilution. In the case of films deposited under the condition of highly diluted silane, microcrystalline states are formed accompanying remarkable decreases in the optical gap, the activation energy of the dark conductivity, and the photoluminescence intensity. However, it is significant that the room‐temperature photoconductivity is not critically dependent on microcrystalline formation. The temperature dependence of the photoconductivity is drastically different depending on whether the film is in an amorphous or microcrystalline state.