It has been reported that brain tumors show decreased IMP uptake, however, we encountered two cases of meningioma which had initially increased IMP uptake. SPECT was performed at 30 min, 2 hr and 6 hr after intravenous administration of IMP (3 mCi). The delayed images (2 and 6 h) showed decreased IMP uptake. These were convexity and parasagittal meningiomas which had tumor stains at angiography. Although the mechanism of IMP uptake in brain tumor is still unclear, this finding should be considered in the interpretation of IMP-SPECT.