19-F and 31-P nuclear magnetic resonance (NMR) spectroscopy have been used to study the ligand binding process in human hemoglobin. 19-F nuclear magnetic resonance studies of hemoglobin specifically trifluoroacetonylated at cysteine-beta93 have permitted observation and characterization of molecular species containing two and three ligands. The behavior of these intermediate species in response to changes in pH and organic phosphate concentration is not completely consistent with any of the current theories of allostery. A model consistent with the 19-F and 31-P NMR data is proposed.