As concomitant chemoradiotherapy for stage III NSCLC is associated with survival advantage in comparison to a sequential approach, we conducted a phase III randomised study aiming to determine the best sequence and safety of chemotherapy (CT) and chemoradiotherapy (CT-RT), using a regimen with cisplatin (CDDP), gemcitabine (GEM) and vinorelbine (VNR). Unresectable stage III NSCLC patients received CDDP (60 mg/m(2)), GEM (1g/m(2), days 1 and 8) and VNR (25mg/m(2), days 1 and 8) with reduced dosage of GEM and VNR during radiotherapy (66Gy). Two cycles of CT with radiotherapy followed by two further cycles of CT alone were administered in arm A or the reverse sequence in arm B. The study was prematurely closed for poor accrual due to administrative problems. Forty-nine eligible patients were randomised. Response rates and median survival times were, respectively 57% (95% CI: 36-78%) and 17 months (95% CI: 9.3-24.6 months) in arm A and 79% (95% CI: 64-94%) and 23.9 months (95% CI: 13.3-34.5 months) in arm B (p>0.05). Chemotherapy dose-intensity was significantly reduced in arm A. Grade 3-4 oesophagitis occurred in 5 patients. One case of grade 5 radiation pneumonitis was observed. In conclusion, chemoradiotherapy with CDDP, GEM and VNR appears feasible as initial treatment or after induction chemotherapy. Consolidation chemoradiotherapy seems less toxic with a better observed response rates and survival although no valid conclusion can be drawn from the comparison of both arms.