The selectivity of a rapid (90)Sr bioassay technique over (241)Am, (238/239)Pu, (210)Po, (137)Cs and (60)Co has been investigated. Similar to (90)Sr, these radionuclides are likely to be used in radiological dispersive devices. The purpose of this study was to demonstrate the degree to which the (90)Sr bioassay technique is free from interference by these radionuclides if present in a urine matrix. The interfering radionuclides were removed (from (90)Sr) by their retention on an anion exchange column. While, recovery of the target radionuclide ((90)Sr) was found to be >or= 90 %, contributions from (241)Am, (242)Pu and (208)Po were found to be <or= 3 % indicating minimal interference from these radionuclides. The breakthrough for (60)Co, however, was found to be <or=19 % indicating that it will have some interference contribution to the (90)Sr measurement if present in the urine sample. As (137)Cs was not retained at all by the anion exchange column, the method as such was not selective over (137)Cs. However, a slight modification of the method through the ammonium molybdophosphate treatment quantitatively removed Cs from the urine sample, thereby; making it selective for (90)Sr despite any (137)Cs that is present.