Ti-6Al-4V matrix composite reinforced with TiB and TiC particulates was prepared and hydrogenated. Isothermal compression tests were carried out at the deformation temperatures ranging from 750 degrees C to 900 degrees C and strain rate ranging from 0.01 s(-1) to 1 s(-1). The effects of hydrogen concentration, deformation temperature and strain rate I on flow stress-strain curves and microstructure evaluation were studied. Hydrogen decreases the deformation temperature at least 100 degrees C or enables the composite to deform at a higher strain rate at the same flow stress level. Hydrogen improves dynamic recrystallization of cc phase and accommodation deformation between reinforcements and matrix. Optimum hydrogen concentrations at different deformation temperatures were determined. The strain rate sensitivity index and apparent activation energy of the composite with 0 wt.% H and 0.35 wt.% H were calculated and discussed. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.