The objective of this work is to evaluate the effect of alteration of blood oxygen affinity in patients with sickle cell anemia. It is generally felt that an increase in oxygen affinity will lead to decreased sickling because a larger fraction of hemoglobin will be in the oxy-configuration at a given partial pressure of oxygen. However, diminished oxygen delivery to tissues might be a deleterious effect of increased oxygen affinity. We have developed reliable methods for measuring whole blood oxygen affinity in sickle cell anemia, and have learned that the position and shape of the oxygen dissociation curve of sickle blood is very dependent on the immediate history of the blood sample after venipuncture. Only under very special conditions is the measured value related to the in vivo oxygen transport capability of blood. The rate of sedimentation of SS red cells is exquisitely sensitive to O2 tension. The value of this measurement in identification and evaluation of anti-sickling compounds is being explored. BIBLIOGRAPHIC REFERENCES: Winslow, R.M., Blood oxygen equilibrium studies in sickle cell anemia. Proceedings of the Symposium on Molecular and Cellular Aspects of Sickle Cell Disease, U.S. Dept. of HEW, publication No. (NIH) 76-1007, 1976 pp. 235-256.