Background/aims: This study aimed to demonstrate the efficacy and tolerability of low-dose weekly gemcitabine as a radiosensitizer in unresectable pancreatic cancer patients treated with chemoradiotherapy. Methods: Twenty-four histologically confirmed pancreatic carcinoma patients (female/male: 10/14, median age: 60) were evaluated. Seven (29%) patients received gemcitabine either as a single agent or in combination prior to chemoradiotherapy. Concurrent 75 mg/m(2) gemcitabine was infused weekly. Radiotherapy was delivered to the primary tumor and positive lymphatics with 3D-conformal radiotherapy to a total dose of 4500 cGy. Local progression-free survival, distant metastasis-free survival and overall survival were evaluated by Kaplan-Meier method. Results: Median follow-up was 36 weeks. Median local progression-free survival, distant metastasis-free survival and overall survival were 22 weeks (95% confidence interval [CI]: 5-59 weeks), 19 weeks (95%CI: 6.9-31 weeks) and 36 weeks (95%CI: 28-43 weeks), respectively. All patients completed radiotherapy as scheduled. Concurrent gemcitabine was given fully in 58.3% of patients. Gemcitabine was terminated in four (16.6%) patients due to grade 3 neutropenia (n=1), grade 3 nausea/vomiting (n=2) or patient's reluctance (n=1). Patients with local response and stable disease to chemoradiotherapy revealed a median survival of 39 weeks (95%CI: 30-47.9 weeks) compared to 36 weeks (95%CI: 9.7-62.2 weeks) in patients with locally progressive disease (p=0.52). Pain was improved in 50% of patients. Conclusions: Weekly low-dose radiosensitizing gemcitabine is effective and safe in unresectable pancreatic cancer patients.