ReSi2 thin films were grown on (001) silicon wafers by vacuum evaporation of rhenium onto hot substrates in ultrahigh vacuum. The preferred epitaxial relationship was found to be ReSi2 (100)/Si(001) with ReSi2 ∥Si〈110〉. The lattice matching consists of a common unit mesh of 120 Å2 area, and a mismatch of 1.8%. Transmission electron microscopy revealed the existence of rotation twins corresponding to two distinct but equivalent azimuthal orientations of the common unit mesh. Although the lateral dimension of the twins is on the order of 100 Å, MeV He+ backscattering spectrometry revealed a minimum channeling yield of 2% for a ∼1500-Å-thick film grown at 650°C. There is a very high degree of alignment between the ReSi2 (100) and the Si(001) planes.