The pyrometers used in MBE technology for the measurements of substrate temperature in the case of heterostructure growth can supply additional information, which is indispensable for the growth of laser structures, in particular VCSELs. During the growth of e.g. AlxGa1-xAs/ GaAs heterostructures the thermal radiation emitted from the substrate before being registered by the pyrometer interfere due to multiple reflections on the internal interfaces and the surface of growing structure. This is because of different optical constants of the layers of different composition. That interference produces the oscillations of the pyrometric signal as a function of the growing layer thickens. In this paper the results of pyrometric interferometry studies during the growth of AlxGal-xAs/GaAs laser heterostructures are pr esented. The quantum well separated confinement heterostructures (QW SCH) and vertical-cavity surface-emitting (VCSEL) lasers are analysed. The usefulness of pyrometric interferometry for the control of growth parameters especially for the control of growth rate of individual layers in those structures has been demonstrated.