Fourier transform infrared spectroscopy (FTIR) has been used to study the extent of hydrogen bonding and its temperature dependence in a segmented polyurethane elastomer synthesized from 2,6-toluene diisocyanate, 1,4-butanediol, and poly(tetramethylene oxide) of 2060 number average molecular weight. It is found that the ratio of the molar extinction coefficient for the hydrogen bonded to the free amine stretching vibration is 4.6 and that this ratio is 1.05 for the hydrogen bonded to the free carbonyl stretching vibration. The temperature dependence of the concentration of hydrogen bonded groups is without any discontinuity at the hard segment glass transition temperature, and the enthalpy and entropy of hydrogen bond dissociation are 29 kJ moJ^(- 1) and 64 J mo1^(-1) K^(-1), respectively. An additional absorption band in the carbonyl stretching region at 1726 cm-1 is attributed to an oxidation product of the polyether segment formed during initial sample preparation and subsequent thermal treatment.