B.L.A. and K.K. gratefully acknowledge support under a Materials Research Group Award by the National Science Foundation No. DMR-9001278. Also the software support by Th. Bollmeier is greatly appreciated. The lattice orientations near the interface of chemical vapor deposited diamond films on Si(001) have been studied by orientation imaging microscopy. This technique is based on the automated analysis of electron backscatter Kikuchi diffraction patterns. The electron beamhas been scanned in discrete steps over the reverse side of the diamond film after having removed the substrate. The obtained data have allowed us to determine the texture and to visualize quantitatively the orientational arrangement of and among individual diamond crystallites in the near-interface region. A comparison with the orientation of the substrate has proved the existence of epitaxially nucleated grains. A high amount of twinned diamond has been deduced from the pole figures and verified by analysis of orientation correlations between neighboring crystallites. Moreover, the grain boundary maps have allowed us to monitor and quantify directly the occurring twin boundaries.