We provide an in situ approach to the determination of quantum dots (QDs) size based on the calculated reflection high-energy electron diffraction (RHEED) patterns. We observe the periodic intensity fringes along the RHEED chevron tails predicted earlier by the theoretical model. The calculated and the observed RHEED intensity profiles are analyzed systematically for different QD heights. The periodicity of the intensity fringes is correlated to the average height of QDs. The possibility of monitoring real time the evolution of dot height during the molecular beam epitaxy/chemical beam epitaxy (MBE/CBE) growth of self-assembled QDs is demonstrated. (C) 2008 Elsevier B.V. All rights reserved.