The overgrowth of pre-patterned (100) GaAs substrates by molecular beam epitaxy (MBE) under different substrate temperature and arsenic overpressure conditions has been investigated. The pattern consisted of mesas with vertical side-walls aligned in the [ 0(1) over bar 1 ] direction. The effect of the growth conditions on the Ga adatom migration length and on the resulting competition between neighbouring facets has been observed. The growth profile has been modelled using a surface diffusion model and results indicate that the change in migration length with growth condition is dependent on facet orientation. © 2005 Elsevier B.V. All rights reserved.