Growth of Cr thin films on GaAs(0 0 1) was carried out using molecular beam epitaxy and was investigated by in situ reflection high-energy electron diffraction (RHEED) and ex situ X-ray diffraction (XRD). The results show that there are two competing mechanisms during the growth, and the film structure strongly depends on the growth temperature. The single-crystalline Cr films with the body-centered-cubic (bcc) structure are obtained, with the epitaxial relationship of (0 0 1)[0 0 1](Cr)parallel to(0 0 1)[0 0 1](GaAs) and (0 0 1)[1 0 0](Cr)parallel to(0 0 1)[1 0 0](GaAs).