[en] Testing procedures were developed and reviewed by the National Bureau of Standards (NBS). Laboratory equipment and supplies needed for preparation and distribution of test samples and phantoms were procured. NBS also supplied certified radionuclide standards for use in the intercomparison program. Two rounds of in vivo and in vitro testing are planned. A torso phantom with interchangeable sets of radioactively labeled lungs and a whole-body bottle phantom filled with precise amounts of selected radionuclides in a gelatinous matrix will be shipped to participating in vivo counting facilities. Natural or artificial urine samples spiked with carefully controlled amounts of radionuclides will be shipped to participating in vitro bioassay laboratories for analysis. Procedures to be tested include liquid scintillation counting, alpha spectrometry, beta measurements, fluorescence measurements, and gamma spectrometry