[en] In situ and laboratory gamma-ray spectroscopy measurements were taken in nine scrub oak forests and nine old fields to determine the applicability of in situ analysis in the coastal plain. Data collected at each of the 18 sites included a 2-hr count, soil density and moisture estimates, and vegetation measurements. Samples returned to the laboratory for radiometric analysis included litter and herbaceous vegetation and soil cores. Analysis of the gamma-emitter detection frequencies, concentrations, and burdens showed good to excellent agreement between laboratory and in situ methods. Generally, forests were determined to be superior in situ sampling systems. Laboratory analysis of collected samples may be a superior technique for gamma emitters with low energies, low concentrations, or nonuniform distributions in the soil. Three potential uses of in situ Ge(Li) spectrometers were identified and discussed in terms of their limits and of the replicate ecosystems appropriate for in situ analyses. Although the variety and the biogeochemical cycling regimes of southeastern coastal plain ecosystems complicate in situ analyses, it was concluded that comparable and probably accurate results can be achieved using in situ technology