The anion transport system of the human red blood cell membrane is not well understood. Experiments designed to determine the mechanisms of transport have relied on anion flux or equilibrium binding measurements. We propose to study anion transport by stopped-flow experiments on the interaction of anions and anion transport inhibitors with the transport protein of the red cell membrane. Preliminary experiments on the interaction of anion transport inhibitors with red cell membranes have shown that the time resolution afforded by stopped-flow experiments allows a specification of protein conformations. Analysis of stopped-flow data shows that the commonly accepted model of anion transport inhibition may have to be modified to include interacting monomeric subunits of the dimeric transport protein and allosteric inhibition. The results of the research proposed here will contribute to an understanding of anion transport in red cells as well as having general application to other membrane transport systems.