Stereotactic ablative radiotherapy (SABR) is well tolerated and results in high local control in patients treated for early stage lung cancer. High doses of radiation are possible partly due to daily image guidance, often cone-beam computed tomography (CBCT), allowing for small tumor (GTV) to planning target volume (PTV) margins. Proton therapy limits radiation distal to the Bragg peak and is therefore an attractive modality especially for large, peripheral and centralized tumors. Some proton therapy centers do not have CBCT and rely on orthogonal x-rays/fiducials for localization, prohibiting SABR. The NCIC CTG BR.25 reported on a more moderate hypofractionated course (60 Gy in 15 fractions) with 87% local control. Five years ago, we adopted this fractionation scheme and here we report on our experience. We also developed photon plans to compare dosimetric data. From 12/2012 to 01/2017, 13 patients received hypofractionated lung proton therapy. All patients underwent 4DCT simulation. An internal target volume was delineated on the maximum intensity projection planning CT scan. The ITV was expanded 0.5-1.2 cm radially and 1.0-1.2 cm in the craniocaudal direction. A minimum of 3 treatment fields were utilized. Sixty biologically weighted gray was prescribed to the PTV in 4-5 Gy(RBE)/fraction over 3 weeks. All patients were treated with uniform scanning techniques. Comparative photon plans were created with the same grid size, target coverage requirements, and planning constraints. Toxicity was assessed using Common Terminology Criteria for Adverse Events v4.0. Median follow-up was 27 months (range: 1-48 months). Eleven patients had centralized tumors within 2 cm of the proximal bronchial tree, heart, esophagus, vertebral body, or brachial plexus. Median age was 80 (range: 67-91). Four patients (31%) had T1 lesions. The median GTV measured 19.8 cm3 (range: 2.3-208.6 cm3). Mean PTV V95% coverage was 96% (range: 88%-100%). Actuarial local and regional controls were 92% and 85%, respectively. Distant metastasis rate was 15%. There were no local or regional failures noted when the primary GTV was less than 35 cm3. No grade 3-5 toxicity was observed. One patient (7.6%) developed acute grade 2 lung toxicity. No treatment breaks were required for any patient. Lung V5,V10,V20, and mean were lower with proton versus photon plans (29% vs 16%, 17% vs 12%, 12% vs 9%, 6 Gy(RBE) vs 4Gy; p <.01). Esophagus and heart mean were also lower in the proton plans (7 Gy(RBE) vs 2Gy, 6 Gy(RBE) vs 0.6Gy; p<.02). Esophagus, heart, spinal cord, and brachial plexus maximum were not significantly different between proton and photon plans. Hypofractionated proton therapy was well tolerated and effective. For centers without CBCT, this regimen may be a reasonable treatment option especially for large, centralized tumors. As these treatments were well tolerated, further dose intensification may be feasible. Longer term follow up is needed to validate these preliminary outcomes.