The homotropic and heterotropic effects of isolated Hb Willamette were studied using an automatic recording oxygen equilibrium analyzer. The results indicate that Hb Willamette displays normal intrinsic oxygen binding in the stripped condition. An apparent decrease of the Bohr effect is explained by the decrease of allosteric effects in this abnormal hemoglobin. Furthermore, the lack of clinical manifestations in the original patient is consistent with the red cell oxygen equilibrium studies.