Ten patients with histologically proven osteogenic sarcoma received multiple courses of intra-arterial chemotherapy. Patients received 2-3 mCi 99mTc macroaggregated albumin (MAA) infused through indwelling arterial catheters prior to, during and after the chemotherapy, and static images of tumor beds and lungs were taken and compared with contrast angiographic findings. Of the 31 studies to evaluate tumor vascularity, 26 agreed and five showed discrepancies. In general, decreased tumor vascularity, as represented by reduced MAA uptake by the tumor, corresponded to decreased tumor size and to increased tumor calcification seen on radiographs. Twenty-six of the 31 lung-imaging studies also revealed agreement between decreasing tumor vascularity, based on decreasing MAA tumor uptake, and decreasing lung uptake of the radioactivity. Decreased lung uptake of the activity on the last follow-up study in eight patients corresponded to reduced tumor involvement and improved patient performance status.