The objective of this investigation was to determine the effect of wrist guard use on all upper-extremity injuries in snowboarders. This matched case-control study was conducted at 19 ski areas in Quebec, Canada. Cases were 1,066 injured snowboarders who reported upper-extremity injuries to the ski patrol during the 2001-2002 season. Controls were 970 snowboarders with non-upper-extremity injuries who were matched to cases on ski area and the nearest date, age, and sex, in that order. The response rate was 71.8% (73.5% for cases and 70.1% for controls). Cases were compared with controls with regard to wrist guard use. The prevalence of wrist guard use among snowboarders with hand, wrist, or forearm injuries was 1.6%; for those with elbow, upper arm, or shoulder injuries, it was 6.3%; and for controls, it was 3.9%. Thus, wrist guard use reduced the risk of hand, wrist, or forearm injury by 85% (adjusted odds ratio = 0.15, 95% confidence interval: 0.05, 0.45). However, the adjusted odds ratio for elbow, upper arm, or shoulder injury was 2.35 (95% confidence interval: 0.70, 7.81). These results provide evidence that use of wrist guards reduces the risk of hand, wrist, and forearm injuries but may increase the risk of elbow, upper arm, and shoulder injuries.