We have studied the vibrational relaxation of the H2O bending mode in an H2O:HDO:D2O isotopic mixture using infrared pump-probe spectroscopy. The transient spectrum and its delay dependence reveal an anharmonic shift of 55+/-10 cm(-1) for the H2O bending mode, and a value of 400+/-30 fs for its vibrational lifetime. (C) 2004 American Institute of Physics.