60 patients with lateral epicondylitis were randomized to an injection into the extensor carpi radialis brevis (ECRB) of either botulinum toxin type A (BoNT-A) or placebo. Patients were assessed after 30 and 90 days. The primary outcome was the rate of patients who experienced a minimum 50% reduction in pain on a visual analog scale. Additional outcomes investigated included the rate of patients who experienced interference with daily activities, sporting events, and professional activities, the incidence of side effects, and the rate of patients who requested additional treatment after 90 days was documented. Results demonstrated a significantly higher rate of patients in the BoNT group compared to the placebo group who experienced 50% or more reduction in pain after 90 days. Other outcomes which significantly favoured the BoNT-A group were interference with daily activities or rate of request for subsequent treatment. The rate of side effects did not significantly differ between groups.