Each of 36 patients was studied with two separate brain scans performed sequentially after the injection of 20 mCi of 99mTc-pertechnetate or 20 mCi of 99mTc(Sn)-diphosphonate. The resulting scans were qualitatively compared, and lesion-to-nonlesion ratios of activity determined. Diagnoses were established by clinical criteria and were supported in the majority of cases by computerized axial tomography or roentgen angiography or both. Histologic confirmation was available in five cases of tumor and in the single cases of subdural hematoma and cerebral abscess. Of 22 cerebral infarctions, 15 were better demonstrated with 99mTc-(Sn)-diphosphonate than with 99mTc-pertechnetate. Of the seven remaining cases, three were visualized equally well with each agent, and three were better demonstrated with 99mTc-pertechnetate. One was not seen with either agent. Of the 12 tumors, 11 were visualized better with 99mTc-pertechnetate than with 99mTc-(Sn)-diphosphonate while in one case the lesion was seen equally as well with both agents. In no case was a lesion definitely seen with one radiopharmaceutical and not with the other. These results indicate that this dual method is helpful in differentiating gliomas and metastases from cerebral infarctions.