Breathing retraining is used increasingly throughout the world by many patients with asthma in addition to their usual medical care. We undertook a systematic review of the literature in order to determine the effectiveness of breathing retraining in the management of asthma. Six randomised-controlled trials were identified that involved breathing retraining in asthma. Due to the variation in reported trial outcomes, limited reporting of study data and small number of included trials it was not possible to draw any firm conclusions as to its effectiveness. However, outcomes that were reported from individual trials do show that breathing retraining may have a role in the treatment and management of asthma. Further large-scale trials using breathing retraining techniques in asthma are required to address this important issue.