The radioactivity in 2 persons occupationally exposed to both 90Sr and 226Ra was measured at 7 laboratories using whole-body counters. In addition to 40K and 137Cs, 90Sr and members of the 226Ra series were found in both individuals in amounts corresponding to 30-100% of the maximum permissible burdens (2 Ci 90Sr, 0. 1 Ci 226Ra). The techniques used for the measurements and the results obtained are compared. Satisfactory agreement was ultimately established between the various centers, and it is concluded that in such persons the amounts of 90Sr, 214Bi, 40K, and 137Cs can be determined with an accuracy of 10-20%.