Surfaces of microcrystalline silicon films prepared by the glow discharge method have been investigated by a scanning tunneling microscope (STM) in air. Grain‐like structures of 30–80 nm size which correspond to transmission electron microscope data have been observed. The film surface was found to be geometrically rather flat but the structure was observed electrically, that is, the resistivity seemed to be inhomogeneous due to preferential oxidation. Also, degradation of STM images of a HF‐etched microcrystalline silicon surface has been observed for the first time.