The distribution of the partial pressure of carbon dioxide in surface waters of the Atlantic, Pacific, and Indian oceans has been determined from 24 months of continuous measurements obtained on oceanic expeditions of the Scripps Institution of Oceanography in all three oceans, supplemented by 9 months of similar measurements and 55 discrete analyses obtained on other expeditions in the Atlantic Ocean and near the west coast of South America. The data, most of which represent summer conditions, are displayed on a chart that is the first to be prepared for the world's oceans. In the Pacific and Atlantic oceans pronounced belts of high pressure appear near the equator. The Pacific belt is far more extensive than the Atlantic, but the patterns are similar and both are clearly defined. In the Indian Ocean during the northern summer the pressure diminishes southward from India to 30°S with no high-pressure belt near the equator. In the subtropicals of all oceans the pressure tends to be low except in coastal areas where upwelling occurs. In polar areas patterns appear to be more complicated and are uncertain because the data are too few to establish seasonal variability.