Absorbance spectra for the hemoglobin species, including oxy-, deoxy-, carboxy-, and methemoglobin in the midinfrared region, are presented. The absorbance spectra of all species in aqueous solution are similar with absorption bands centered at approximately 3280, 3080, 2964, 1653, 1541, 1456, 1396, 1302, 1248, and 1105 cm−1. The relationship of the midinfrared absorption bands to the near-infrared absorption bands of the same four hemoglobin species is discussed. © 1997 John Wiley & Sons, Inc. Biospect 3: 225232, 1997