In comparison with other geologic terranes, the Coastal Plain of the eastern and southern United States is a region of low to moderate radon potential with local areas of high radon potential. Analyses were made of soil radon concentrations, soil permeability, and equivalent uranium concentrations. Descriptions of soil profiles include grain size analyses, relative moisture concentrations, and mineralogy. Data from Texas, Alabama, and New Jersey indicate that Cretaceous and lower Tertiary glauconitic sands. Cretaceous and Tertiary chalks, carbonaceous shales, and phosphatic sediments have the highest radon-producing potential. Marine limestones and quartz sands have the lowest radon-producing potential. More than half the soil radon concentrations measured were less than 500 pCi/L; however, 20% of the soil radon concentrations were 2,000 pCi/L or more. The highest soil radon concentration sampled was 16,200 pCi/L measured in the glauconitic sands of the Navesink Formation in New Jersey.