The routine occupational exposure of airport cargo workers to radiation from radioactive packages passing through the cargo docks of St. Louis International Airport has been studied as part of a national study of six major airports. Exposures were determined using thermoluminescent dosimeters with a resolution of better than 0.1 mR. The data were collected during sixteen selected eight-hour workshifts over a period of one month. The study shows that a major part of cargo workers' exposure arises from direct encounter or “contact” with radioactive packages during processing, handling, and moving of these packages, but some of the exposure is incidental. Cargo workers who handle radioactive packages receive weekly exposures in the range between 3 and 9 mR above background (about 1.2 mR); on single shifts individual workers receive exposures of up to 5 mR. The “average contact exposure rate”, averaged over all workers handling radioactive packages, stays consistently between 10 and 16 mR/hr for single shifts. The results obtained during the St. Louis study provide a quantitative basis for making rough estimates of exposure at other airports. Some of the implications for processing and handling of radioactive packages at airports are discussed.