A random clinical trial was performed to determine the immediate effects of early ankle mobilization on active duty military members with moderate and severe lateral ankle sprains. Sixty-four subjects were randomly allocated to one of three treatments: a plaster cast, an air-stirrup (Aircast Inc., Summit, New Jersey), or an elastic wrap. Each intervention lasted 2 weeks followed by 3 weeks of rehabilitation. Subjects who were allowed early mobilization returned to work and running significantly sooner than those placed in plaster casts (p = 0.029). Swelling (p = 0.009) and pain (p < 0.001) decreased while range of motion increased (p = 0.027) in the early mobilization groups. Between the mobilization groups, those in the elastic wrap performed as well as those in the air-stirrup.