Purpose: To assess the accumulated dose and the toxicity after reirradiation for tumors in the lung using non-rigid registration. Material and methods: Twenty patients with a tumor in the lung were reirradiated with or after stereotactic radiotherapy. The summed dose distribution was calculated using non-rigid registration. All doses were recalculated to an equivalent dose of 2 Gy per fraction (EQD2). The median follow-up time was 12 months (range 2-52). Results: The median D-max of the lung in the summed plans was 363 Gy(3) (range 123-590). The median accumulated V20 of the lungs was 15.2%. Seven patients had in the heart and the trachea an accumulated dose >= 70 Gy(3), with a median D-max of the heart of 115 Gy(3) and 89 Gy(3) for the trachea. Eight patients had in the esophagus an accumulated dose >= 70 Gy(3), with a median accumulated dose of 85 Gy(3). No grade 3-5 toxicity was observed. Conclusion: Reirradiation of the lung with or after stereotactic radiotherapy is feasible to a median D-max of 363 Gy(3) to the lung, as low toxicity was observed. (c) 2013 Elsevier Ireland Ltd. All rights reserved.