This work summarizes the observations made on the variation and time evolution of the reflectance anisotropy signal during the MOVPE growth of GaInP nucleation layers on Germanium substrates. This in situ monitoring tool is used to assess the impact of different nucleation routines and reactor conditions on the quality of the layers grown. This comparison is carried out by establishing a correlation between reflectance anisotropy signature at 2.1 eV and the morphology of the epilayers evaluated by atomic force microscopy (AFM). This paper outlines the potential of reflectance anisotropy to predict, explore, and therefore optimize, the best growth conditions that lead to a high quality III-V epilayer on a Ge substrate. (C) 2010 Elsevier B.V. All rights reserved.