In 1995, we audited the outcome following Gartland's type III supracondylar fractures of the humerus in children. Closed reduction under anaesthesia (MUA) and cast immobilisation was the treatment of choice, with the treatment changed whenever displacement occurred. The result of the audit showed that 86% of cases were treated with this method. The rate of re-operation was 45.6%. Cubitus varus deformity developed in 50% of cases. Guidelines were introduced in order to abandon the use of MUA and cast immobilisation for type III fractures. The guidelines recommended treating these fractures with rigid fixation using Kirchner (K) wires. A re-audit was conducted in the year 2000 to study the impact of introducing the guidelines. The rate of compliance was 64%. The re-audit showed a significant drop in the rate of re-operations from 45.6 to 17.7% (P = 0.0043), and a significant drop in the incidence of cubitus varus from 50 to 6.6% ( P < 0.0001). The results of the re-audit suggest that practice guidelines can have a major impact on clinical practice.