Simultaneous emission and transmission tomography was performed after the injection of [99mTc]MAA in 30 patients undergoing intra-arterial chemotherapy to nonhepatic sites to determine the accuracy of catheter placement. The transmission and emission data were reconstructed in transverse, and optionally, coronal and sagittal planes. The correlation of the emission scan with the reconstructed transmission data allowed accurate anatomical localization of the infusate distribution. In seven patients, catheter placement resulted in perfusion to nontumor sites, and hence required repositioning. MAA accumulation was seen in the lungs of all patients, regardless of tumor site, indicating arterio-venous shunting of the MAA. The degree of uptake in the lungs was quantified from planar anterior/posterior thorax images in terms of injected dose in ten patients, with values of 5-50% of injected dose present in the lungs. The technique provides a noninvasive means of accurately determining regional perfusion of chemotherapeutic agents delivered intra-arterially.