The experience with pancreatic, biliary and gastric cancer in the US has demonstrated that IORT is technically a feasible and therapeutically relatively safe modality. However, much research remains to be done. The toxicity in humans of single large dose radiation to normal tissue has not been firmly established. Clinical studies must be able to demonstrate the efficacy of IORT as well as a therapeutic advantage for this approach. IORT is potentially a very effective adjuvant therapy in treating tumors which are technically difficult to treat surgically or which have a high rate of recurrence following radical surgery. The combination of surgery and IORT may improve local control of the tumor by removing gross disease and identifying areas of potential risk for recurrence. Regional and distant failure, however, remains a problem. Because of this, future investigations are underway to combine chemotherapy with IORT, surgery and EBRT. The effectiveness of IORT needs to be established with prospective randomized trials. The appeal of this procedure is demonstrated by its rapidly growing popularity, and this very appeal requires that the value of the procedure be determined.