To improve the target coverage and normal tissue sparing of intensity-modulated radiotherapy (IMRT) for mesothelioma after extrapleural pneumonectomy.Thirteen plans from patients previously treated with IMRT for mesothelioma were replanned using a restricted field technique. This technique was novel in two ways. It limited the entrance beams to 200 degrees around the target and three to four beams per case had their field apertures restricted down to the level of the heart or liver to further limit the contralateral lung dose. New constraints were added that included a mean lung dose of or=5 Gy of or=20 Gy, and volume receiving >or=5 Gy with the new technique was 6.6 Gy, 3.0%, and 50.8%, respectively, compared with 13.8 Gy, 15%, and 90% with the previous technique (p or=20 Gy, and volume receiving >or=5 Gy, respectively.Restricted field IMRT provides an improved method to deliver IMRT to a complex target after extrapleural pneumonectomy. An upcoming Phase I trial will provide validation of these results.