GaSb epilayers were grown on GaAs(0 0 1) vicinal substrate misoriented towards (I 1 1) plane by solid-source molecular beam epitaxy (MBE). The relative tilt between GaSb epilayer and GaAs substrate was studied using high-resolution X-ray diffraction (HRXRD). It was demonstrated that the tilt of the 30 nm thick GaSb film was 0.32 degrees, which was a simple geometrical consequence of 7.8% lattice mismatch. For the 1000 nm thick film, tilt rose to 0.45 degrees, and the increase of tilt was the result of the forming of 60 degrees misfit dislocations (MDs). In contrast to the phenomenon in low-misfit heteroepitaxy system, tilts induced by 60 degrees MDs in our samples were positive (i.e. away from the surface normal) and we attributed the diversity to the different formation mechanisms of 60 degrees MDs. The tilt study gave us another way to investigate the type and the formation mechanism of the MDs. (C) 2007 Elsevier B.V. All rights reserved.