Two-color infrared pump-infrared probe spectroscopy has been used to measure vibrational relaxation times (T-1) for the CO stretching vibrations of carboxyhemoglobin (HbCO), carboxymyoglobin (MbCO), and carboxyprotoheme, all in D2O at 300 K. The times are fast (17-31 ps) compared to most previously measured metal carbonyl T-1 times. The CO relaxation is found to be somewhat faster in HbCO and MbCO than in PCO. The transient infrared spectra and anisotropy were also measured.