Background Preclinical and phase I data suggest gemcitabine to be a potent radiosensitiser. This multicentre study addressed whether the addition of low dose gemcitabine to radical radiotherapy improved 2 year event-free survival in patients with medically inoperable stages I–II non-small cell lung cancer. Aim To determine whether low dose gemcitabine increased event–free survival in patients with T1-2 N0-1 M0 NSCLC deemed unfit for surgery. Methods Patients with T1-2 N0-1 M0 NSCLC deemed unfit for surgery were randomised to 3D conformal radiotherapy delivering 55 Gy in 20 fractions over 4 weeks to known sites of cancer with (Arm B) or without (Arm A) 100 mg/m2 weekly gemcitabine. Results Study entry was terminated early because of slow accrual. 111 patients were randomised between March 2003 and December 2005, of whom 4 withdrew consent and 2 were lost to follow-up. Median age was 75 (range 49–88) years and 67 (63%) were male. 86 (81%) were PS 0–1 and 31 (30%) Charlson index 2 or greater. Event-free survival in arm A and B, respectively, was 42% and 46% at 2 years and 20% and 31% at 5 years (p = 0.72), while overall survival was 56% and 52% at 2 years and 20% and 33% at 5 years (p = 0.87). Two deaths from accelerated interstitial lung disease were seen in arm B, but toxicity was otherwise mild. Conclusion No evidence of an improvement in event-free survival was seen with the addition of weekly gemcitabine at this dose for patients with early stage NSCLC unfit for surgery, although the power of the study was low.