[en] A nationwide, two-round bioassay intercomparison study to test the analytical performance of both in-vitro and in-vivo bioassay laboratories and determine their ability to meet the minimum performance criteria specified in the draft American National Standards Institute (ANSI) Standard is being performed. Round One is the Pilot Study involving a small number of voluntarily participating laboratories. Round Two will involve a larger number of laboratories and will expand on the results of Round One. This report is a review of the methodology and results of Round One. Test samples of artificial urine containing precisely known quantities of certain radionuclides were sent to 19 bioassay laboratories, and 16 of those returned analysis data. Results show that some of the participating laboratories had difficulty meeting the performance criteria specified in the current draft ANSI Standard N13.30. 24 references, 1 figure, 11 tables