Laboratory intercomparison studies involving samples of most environmental media are conducted on a continuing basis by the U.S. Environmental Protection Agency’s (EPA) National Environmental Research Center-Las Vegas. These studies enable the EPA to assess the precision and accuracy of radioassay procedures for environmental samples. The data from a recent six-month study to assess the quality of radionuclide measurements in milk indicate that the measurements of 30 federal, state, and private laboratories compare favorably with those of 10 reputable international laboratories. However, the data also indicate a need for improved analytical performance, the adoption of standard reference methods, more frequent instrument calibration, and better quality control in all radio-analytical procedures.