Michigan repealed a 35-year mandatory helmet law on April 13, 2012. We examined the early clinical impacts at a level 1 trauma center in West Michigan.Retrospective cohort study comparing outcomes among motorcycle crash victims in a 7-month period before and after the helmet law repeal.One hundred ninety-two patients were included. After the repeal, nonhelmeted motorcyclists rose from 7% to 29% (P < .01). There was no difference in mortality rate after admission; however, crash scene fatalities increased significantly. Intensive care unit length of stay, mechanical ventilation time, and cost of stay were also higher in the nonhelmeted cohort (P < .05).Our study highlights the negative ramifications of repealing a mandatory helmet law. Motorcyclists not wearing helmets increased significantly in a short period of time. Nonhelmeted motorcyclists more frequently died on the scene, spent more time in the intensive care unit, required longer ventilator support, and had higher medical costs.