The equilibrium hydrogen surface coverage on Si(100) during silicon epitaxy using SiH4has been measured in a rapid thermal chemical vapor deposition reactor. The hydrogen coverage could be ‘‘frozen out’’ completely on the surface by a rapid cool‐down and pump‐down of the reactor up to temperatures of &bartil;575 °C; at temperatures above 575 °C only partial ‘‘freeze‐out’’ is achieved. Surface hydrogen was titratedinsituusing the reactor as a thermal desorption spectrometer. Epitaxial silicon films were grown in the temperature range 450–700 °C and the film growth kinetics was correlated with the equilibrium hydrogen coverage. The growth mechanism changes from the low‐temperature regime, where the surface is hydrogen covered, to the high‐temperature regime, where the surface is essentially clean.