Atomic resolution ultrahigh-vacuum scanning tunneling microscopy studies of chemical-vapor-deposition-grown epitaxial diamond (100) films are reported. After growth, the surface of the epitaxial films is amorphous at the atomic scale. After 2 min of exposure to atomic hydrogen at 30 Torr; the surface is observed to consist of amorphous regions and (2x1) dimer reconstructed regions. After 5 min of exposure to atomic hydrogen, the surface is observed to consist mostly of (2x1) dimer reconstructed regions. These observations are compared with a recent model for chemical-vapor-deposition diamond growth. Tunneling current versus voltage spectroscopy of undoped and boron-doped epitaxial diamond (100) films is also reported.