Background: The use of various types of radioactive drugs has increased the usefulness of nuclear medicine. The efficiency of the labeling radioactive isotope ^99mTc is crucial for the accuracy and reliability of an examination. We conducted a survey on the quality control (QC) of radioactive isotopes (RI) by measuring their purity. Materials and Methods: The QC (always or necessary) of radiopharmaceuticals was confirmed in 12 medical institutions in a metropolitan area. The radiochemical purity (RCP) of ^99mTc-HDP and ^99mTc-phytate was determined based on the measured radionuclide purity of ^99mTc containing ⁹⁹Mo. In addition, the effect of time after labeling and time after elution was analyzed. Results: None of the 12 hospitals regularly performed QC, and five hospitals administered QC when necessary. The average of 30 measurements of the ⁹⁹Mo content in ^99mTc from three manufacturers was 0.0109 for A, 0.0121 for B, and 0.0114 for C. The average labeling efficiency was 96.02% for ^99mTc-HDP and 94.97% for ^99mTc-phytate after labeling. The labeling efficiency of ^99mTc-HDP with different times after elution was 97.56%, 95.41%, 94.86%, 93.76%, and 91.89% after 0.5, 2, 4, 6, and 8 h, respectively, and that for ^99mTc-phytate was 97.21%, 97.21%, 94.42%, 93.35%, and 89.91% after 0.5, 2, 4, 6, and 8 h, respectively. Conclusion: We analyzed the degree of maintenance needed for labeling efficiency. The degree of change should be provided to the clinical practitioner as basic data for the QC of the radiopharmaceutical.