We have grown iron silicides on Si(110) substrates by reactive deposition epitaxy (RDE) for different thermal treatments and investigated the phase transitions and crystallographic relationships between the silicide films and Si(110) substrates through a detailed analysis of reflection high-energy electron diffraction (RHEED) patterns. The RHEED patterns show that beta-FeSi2 is grown epitaxially on Si(110) at the initial stage of RDE growth. With increasing film thickness, beta-FeSi2, epsilon-FeSi, and the pseudomorphic phase gamma-FeSi2 and/or FeSi1+x (0 less than or equal to x less than or equal to I) in a defect CsCl structure are observed on Si(110) depending on the thermal treatment. By depositing Fe at 600 degrees C and annealing at 730 degrees C, beta-FeSi2 is formed in islands with facet planes beta-FeSi2(<(1)over bar 00>)parallel to Si(221) and beta-FeSi2(<(1)over bar 00>)parallel to Si(221), and a base plane beta-FeSi2(<(4)over bar 10>)parallel to Si(110). The peculiar beta-FeSi2(<(4)over bar 10>) plane is parallel to the Si(110) surface because it offers a better lattice match to the Si(110) surface than the other planes.