Summary: This report discusses Multilateral Development Banks (MDB), which provide financial support for projects and programs that promote social and economic progress in developing countries. GAO provides (1) summaries of each bank's mission, function, and operations; (2) key bank financial data covering the last three fiscal years; and (3) information on the U.S. investment in capital and voting percentages in each MDB. GAO found that MDBs are autonomous international financial entities that finance economic and social development projects and programs in developing countries. The MDBs primarily fund these projects and programs using money borrowed from world capital markets or money provided by the governments of member countries. MDBs enable developing countries to access foreign currency resources on more advantageous terms than would be available to them on the basis of their own international credit standing. The MDBs provide assistance in the form of loans, equity investments, loan and equity guarantees, and technical assistance. Direct lending is the primary vehicle of development assistance. The United States is the largest member in most of the MDBs discussed in this report, contributing significant amounts to support the missions of the MDBs and subscribing a significant amount to MDBs' callable capital.