Tetanus infection is caused by the Clostridium tetani bacterium, which can enter the body through a wound or puncture in the skin. Patients who present to an emergency department (ED) with a laceration, wound or bite require a risk assessment to determine whether the wound is clean, tetanus prone or high-risk tetanus prone. Those assessed as tetanus prone or high-risk tetanus prone, with an uncertain or inadequate immunisation history, should receive tetanus prophylaxis treatment. However, some patients receive this treatment unnecessarily. This article describes a service evaluation that explored whether practice in one ED was contributing to potentially avoidable tetanus prophylaxis treatment. The article outlines the results of a five-year retrospective database review, which determined that 18% of all tetanus prophylaxis treatments delivered in the ED during that period were unnecessary. The author makes some recommendations to improve practice.