N-isopropyl p-iodoamphetamine (I-123 IMP) was used in two patients with previous unilateral basal ganglia infarcts documented by CT of the head. Tomographic images obtained with a commercially available rotating gamma camera equipped with a long-bore collimator showed corresponding areas of decreased uptake in the head of the caudate nuclei. Detection of such small areas of decreased perfusion is possible using SPECT and I-123 radiolabeled IMP.