Chemical vapor deposition (CVD) of boron from BCl3 and Hz was investigated in a dual-impinging jet reactor which was connected to an FT-IR spectrometer for on-line chemical analysis of the reactor outlet stream. Formation of the intermediate, BHCl2, during CVD of boron on a hot tungsten substrate was experimentally verified, Boron deposition started at substrate temperatures of around 750 degrees C and showed a significant deposition rate increase with an increase in temperature. At a surface temperature of 1350 degrees C, fractional conversion of BCl3 to B and BHCl2 was found to be around 0.6 and 0.2, respectively. At temperatures less than 1100 degrees C, fractional conversion of BCl3 to BHCl2 was found to be higher than the fractional conversion to boron. Formation of BHCl2 occurs in the gas phase even at temperatures lower than 750 degrees C. Contribution of surface reactions to the formation of BHCl2 increases with an increase in temperature.