Protons differ from standard photon radiation due to its physical properties leading to a lack of exit dose. This property affords the potential for improved outcomes based on toxicity or opportunities for dose escalation. However, in spite of the promise, clinical data remains lacking regarding benefit. Further confounding the issue is the increased cost of proton therapy related to the high capital cost. In this presentation, we will review the rationale for protons, current status of data, and ongoing research efforts.