Personal or nonessential information may be redacted at the editor's discretion.

Background Gun shows are an important source of firearms, but no adequately powered studies have examined whether these events are associated with increases in firearm injuries. Objective To determine whether gun shows are associated with short-term increases in locally occurring firearm injuries and whether this association differs by the state in which the gun show occurs. Design Quasi-experimental. Setting California. Study Population Individuals in California within driving distance of gun shows. Measurements Gun shows in California and Nevada between 2005 and 2013 (n = 915 shows) and rates of firearm-related deaths, emergency department visits, and inpatient hospitalizations in California. Results Compared to the two weeks before gun shows occurred, post-show firearm injury rates remained stable in regions near California gun shows but increased from 0.67 (95% CI, 0.55 to 0.80) to 1.14 (95% CI, 0.97 to 1.30) per 100,000 in regions near Nevada shows. After adjustment for seasonality and clustering, California shows were not associated with increases in local firearm injuries (RR, 0.99 [95% CI, 0.97 to 1.02]), but Nevada shows were associated with increases in injuries occurring in California (RR, 1.69 [95% CI, 1.16 to 2.45]). The pre-post difference was significantly higher for Nevada shows compared to California shows (Ratio of RRs, 1.70 [95% CI, 1.17 to 2.47]). The Nevada association was driven by significant increases in interpersonal violence firearm injuries (RR, 2.23 [95% CI, 1.01 to 4.89), but corresponded to a small increase in absolute numbers. Non-firearm injuries served as a negative control and were not associated with California or Nevada gun shows. Results were robust to sensitivity analyses. Limitation We only examined firearm injuries in California, and gun show occurrence was not randomized. Conclusion Gun shows occurring in Nevada, but not California, are associated with local, short-term increases in firearm injuries in California. Differing associations for California versus Nevada gun shows may be due to California’s stricter firearms regulations.