OBJECTIVES: To measure the frequency and nature of injuries occurring in competitive matches since professionalism was introduced in rugby union. METHODS: The cohort study previously conducted in players from senior rugby clubs in the Scottish Borders in 1993-1994 when rugby union was an entirely amateur sport was repeated in 1997-1998. The same injury definition, outcome criteria, and method of calculating playing hours were used. In total, 803 (84%) of 960 eligible players participated, including all 30 adult players who played professionally for the Scottish Rugby Union or Border Reivers District. The 576 injury episodes in 381 of these players in competitive matches were compared with the 373 injuries in 266 players out of 975 (94%) who were eligible and registered with the same senior rugby clubs in 1993-1994. Outcomes were the occurrence of injury episodes, days away from playing or training for rugby, and time lost to employment or attendance at school/college as a consequence of being injured. RESULTS: The proportion of players who were injured almost doubled from 1993-1994 to 1997-1998, despite an overall reduction of 7% of the playing strength of participating clubs. Period prevalence injury rates rose in all age specific groups, particularly in younger players. This translated into an injury episode every 3.4 matches in 1993-94, rising to one in every 2.0 matches in 1997-1998. An injury episode occurred in a professional team for every 59 minutes of competitive play. Professional players sustained a higher proportion of recurrent injuries, particularly in the early part of the season. Some 56% of all their days lost to the game were caused by injuries to the muscles, ligaments, and joints of the knee, hip, and thigh. CONCLUSIONS: The introduction of professionalism in rugby union has coincided with an increase in injuries to both professional and amateur players. To reduce this, attention should be focused on the tackle, where many injuries occur. The International Rugby Board should place a moratorium on the use of protective equipment in competitive matches until its contribution to player morbidity has been fully assessed.