High Reliability Organizations (HROs) are organizations that have potentially catastrophic consequences for failure, yet perform with very low levels of failure under demanding conditions (Gaba et al. 2003). Examples of HROs include commercial and military aviation, re ghters, and the nuclear power industry. Medicine has many of the characteristics of these HROs in that it is oen demanding (e.g., in the emergency room), complex, and failures can easily lead to permanent injury or death. Single critical errors in radiation therapy can lead to multiple deaths. What keeps medicine in general and radiation therapy in particular from being considered an HRO is its relatively high error rate.