This study is designed to assess the toxicity and therapeutic effectiveness of concurrent gemcitabine and radiotherapy in patients with unresectable pancreatic cancer. Concurrent gemcitabine (400 mg/m(2)/wk) in six weekly cycles starting on d 1 of radiotherapy (50.4 Gy; 1.8 Gy/fraction/d; 5 d/wk) was prescribed on 22 patients with locally advanced pancreatic cancer. Patients were analyzed with regard to radiological response on computerized tomography, overall survival, and toxicity. Twelve (55%) patients completed the prescription of six gemcitabine cycles and 50.4 Gy radiotherapy; while 10 (45%) received one to five cycles of gemcitabine owing to neutropenia. All patients experienced abdominal discomfort during treatment and three patients required medical intervention. Other toxicities reported were nausea in 13 patients (60%), grade 3 vomiting in 3 (14%). Radiological response evaluations were as follows: complete, 2 (9%); partial, 9 (41 %); stable, 7 (32 %); and progressive, 4 (18 %). Median survival was 8.7 mo. Combination of weekly gemcitabine (400 mg/m(2)) and radiotherapy provided response in 50% of the patients but was associated with severe toxicity resulting in incomplete delivery of the planned chemotherapy.