To identify factors associated with an increased risk of ocular air gun injury among 5- to 19-year-olds. Case-control study. Cases of ocular air gun injury were identified through two ocular trauma registries. Two randomly selected control groups were identified, both through random digit dialing. Air gun-exposed controls had handled an air gun in the previous 12 months, whereas community controls had not. Parents of the cases and controls were contacted for a standardized telephone interview. The study included 124 cases, 237 air gun controls, and 159 community controls. Circumstances of the event, typical air gun use, and demographic characteristics. Cases were 24 times (95% confidence interval, 6.3 to 93.6) more likely to have no adult supervision at the time of air gun use than the air gun controls, almost 12 times (95% confidence interval, 3.3 to 41.1) more likely to have been at a friend's home rather than their own, and five times (95% confidence interval, 1.4 to 20.9) more likely to have been indoors at the time of air gun use. This may indicate that the air gun was handled without a specified purpose, supported by the almost six-fold (95% confidence interval, 2.2 to 14.8) increased risk of injury when the air gun was used for a purpose other than target practice. Unsupervised access to air guns and unstructured air gun use are the principal risk factors for ocular injury. Strategies to educate parents concerning the need to supervise such access may help to reduce this source of preventable vision loss.