Proton beam therapy (PBT) offers compelling advantages in physical dose distribution compared to photon therapy. There are increasing numbers of gantry-based proton facilities worldwide but no such facilities exist in Canada. To access PBT, Canadian patients must travel abroad for treatment at high cost. In the face of limited access, this report seeks to provide recommendations for the selection of patients most likely to benefit from PBT and suggests an out-of-country referral process. METHODS: A systematic literature search for studies between January 1990 and May 2014 evaluating clinical outcomes after PBT. A draft report was developed through review of evidence, externally reviewed, and approved by the Alberta Health Services Cancer Care Proton Therapy Guidelines steering committee. RESULTS: Proton therapy is often used to treat tumours close to radiosensitive tissues, and children at risk of developing significant late effects of radiation therapy (RT). Local control rates with PBT appear similar to or, in some cases, higher than photon RT in uncontrolled and retrospective studies. Randomized trials comparing equivalent doses of PBT and photon RT are not available. SUMMARY: Referral for PBT is recommended for patients being treated with curative intent, with an expectation for long-term survival, and who are able and willing to travel abroad to a proton facility. Commonly accepted indications for referral include chordoma and chondrosarcoma, intraocular melanoma, and solid tumours in children and adolescents occurring in patients with greatest risk of long-term sequelae. Current data do not provide sufficient evidence to recommend routine referral of patients with most head and neck, breast, lung, gastrointestinal tract, and pelvic cancers including prostate cancer. It is recommended that all referrals be considered by a multidisciplinary team to select appropriate cases.