Rugby union is a full contact sport with a relatively high overall risk of injury and a small specific risk of fatal and catastrophic spinal injury. Although catastrophic injuries in rugby union cause public concern and generate strong emotive reactions, the magnitude of society's concern about this type of injury is often dominated by people's perceptions rather than by actual levels of risk. This article assesses published values for the risk of catastrophic injuries in rugby union, evaluates these against the risk standards of the UK Health and Safety Executive (HSE) and compares the values with the risks associated with other common sport and non-sport activities. The assessment showed that the risks of sustaining a catastrophic injury in rugby union in England (0.8/100,000 per year), Ireland (0.9/100,000 per year) and Argentina (1.9/100,000 per year) were within the HSE's 'acceptable' region of risk (0.1-2/100,000 per year), whilst the risks in New Zealand (4.2/100,000 per year), Australia (4.4/100,000 per year) and Fiji (13/100,000 per year) were within the 'tolerable' region of risk (2-100/100,000 per year). The risk of sustaining a catastrophic injury in rugby union was generally lower than or comparable with the levels reported for a wide range of other collision sports, such as ice hockey (4/100,000 per year), rugby league (2/100,000 per year) and American Football (2/100,000 per year). In addition, the risk of catastrophic injury in rugby union was comparable with that experienced by most people in work-based situations and lower than that experienced by motorcyclists, pedestrians and car occupants. Whilst ranking risks provides an effective way of assessing their acceptability, it is recognized that representing risks by a single risk value can be misleading, as account must also be taken of the public's perception of the risks and the inherent differences in the types of risk being considered. However, an acceptable level of risk is often regarded as one that is no greater than the levels of risk that an individual encounters in everyday life. In this respect, the assessment indicated that the risk of sustaining a catastrophic injury in rugby union could be regarded as acceptable and that the laws of the game therefore adequately manage the risk.