Randomized trials of the Gastrointestinal Tumor Study Group have previously demonstrated enhanced survival of patients with locally unresectable pancreatic cancer treated with 5-fluorouracil in combination with radiation therapy compared with that of patients treated with radiation therapy alone. The present study compared the survival of patients treated with multidrug chemotherapy [streptozocin, mitomycin, and 5-fluorouracil (SMF)] versus radiation combined with 5-fluorouracil followed by the same three-drug SMF combination. In 43 patients randomly allocated between these two arms, an improved median survival for the combined-modality therapy (42 weeks) compared with chemotherapy alone (32 weeks) was demonstrated. Overall survival following this combined-modality treatment program (41% at 1 year) was significantly superior to that following SMF chemotherapy alone (19% at 1 year), by a two-tailed log rank test (P less than .02). Serial studies of the Gastrointestinal Tumor Study Group with patients with locally unresectable pancreatic adenocarcinoma have shown that combined-modality therapy is superior to either optimal radiotherapy or chemotherapy alone.