A study of a well-defined group of rugby players was undertaken in Wales to determine whether there has been an increase in the number of serious neck injuries during the past 20 years. None such occurred until a single incident in 1964 and not again until 1974. Since then the injuries have continued at a steady rate of about two per year. The mechanism of the injuries was analysed but no single factor could be identified as being responsible for this sudden increase although tactics in the scrummage played an important part. The importance of flexion injuries is emphasized but it is likely that not all the responsible factors have yet been identified.