One of the first commercial point of inflection thermometry (POINTTM) systems is compared to an IRCON(TM) ModlinePlus Series V pyrometer, and the standard noncontact thermocouple in a Mod Gen II molecular beam epitaxy system. The standard POINTTM system was modified to include a pyrometer as an integral part of the optical system. A series of temperature measurements using these three techniques were compared on GaAs and InP substrates and during the molecular beam epitaxy growth of GaSb layers on a semi-insulating, single-side polished GaAs substrate. It is possible to obtain excellent agreement between the POINTTM system and pyrometer measurements over the effective operating range of the pyrometer (similar to 400-600 degrees C). We concluded that the POINTTM system performed well in its intended mode, which consists of deposition of films with band gaps larger than that of the two substrates GaAs and InP, for which the instrument is calibrated. Furthermore, for deposition of narrow band gap materials, the integration of a transmission (POINTTM) and an emission instrument (pyrometer) Provide a very powerful combination. The present limitations of the POINTTM system and recommendations for improvements will be discussed.