Determining the radiochemical purity of 99Tcm-HMPAO using the standard method suggested by the manufacturer of the HMPAO kit is slow, consuming much of the 30 min useful shelf-life of the radiopharmaceutical. We have compared two new methods (a solvent extraction technique and a method involving a disposable, pre-packed reverse phase chromatography cartridge) with the standard method for determining the radiochemical purity of 99Tcm-HMPAO. There were no significant differences (F test, p less than 0.05) in the results obtained by all three methods. However, the reversed phase chromatography method gave better agreement (correlation coefficient of 0.877) with results obtained using the standard method than did the solvent extraction technique (correlation coefficient of 0.693). The solvent extraction technique took about 10 min to perform whereas the reversed phase chromatography method took only 5 min. Both of the new methods did not achieve complete separation of the secondary, less lipophilic 99Tcm-HMPAO complex from the primary, lipophilic 99Tcm-HMPAO complex but the error introduced was small (typically only 3-5%). The new methods offer the capability of determining the radiochemical purity of 99Tcm-HMPAO quickly, reliably and accurately, prior to administration of the radiopharmaceutical to the patient.