The distribution of middle tropospheric carbon monoxide measure by the Measurement of Air Pollution from Satellites (MAPS) instrument carried aboard the space shuttle is reported. The data represent average mixing ratios in the middle troposphere and are presented in the form of maps that show the carbon monoxide mixing ratios averaged for 6 days of the mission. Comparisons with concurrent, direct measurements taken aboard aircraft show that the inferred concentrations are systematically low by from 20 to 40 percent depending upon which direct measurement calibration standard is used. The data show that there are very large CO sources resulting from biomass burning over South America and southern Africa. Measured mixing ratios were high over northeast Asia and were highly variable over Europe. Reichle, Henry G., Jr. and Connors, Vickie S. and Wallio, H. Andrew and Holland, J. Alvin and Sherrill, Robert T. and Casas, Joseph C. and Gormsen, Barbara B. Langley Research Center ...