Abstract
The properties of the stars believed to be responsible for exciting Herbig-Haro objects are discussed. Various combinations of techniques have been used to indicate specific identifications of exciting stars yet, in very few cases, is there a visible counterpart to these objects. Bolometric luminosities can be estimated reliably from far-infrared observations of the exciting stars but only two can be unambiguously located in the HR diagram. However, the luminosities of all, but one, of these stars can plausibly be attributed to lowmass ("`lM ) protostars viewed in their very earliest phases of evolution. Only R Mon, wita its exceptionally high luminosity, is likely to be a higher mass object.
