The first large scale survey of surface CO concentrations at Southern Hemisphere continental sites is described. Marine sites are compared to sites with a true continental character with the objective to identify different ecological surface conditions in terms of CO concentrations. The marine sites at the Atlantic coast show the lowest concentrations, about 100 ppbv, whereas the sites in the savannah region show concentrations 3 times as large owing to the influence of nearby biomass burning activity. The observations were highly variable, with one result as high as 700 ppbv. These high values are comparable to sites near urban developments. Sites in the Amazonian rain forest show concentrations as low as the coastal sites, on the average, but sporadic peaks have been seen when air masses are brought in from city areas or from large forest fires.