AIM: This paper reports a systematic review of seven studies evaluating the efficacy of cognitive behavioural therapy (CBT) for persistent primary insomnia. BACKGROUND: Insomnia is one of the most common health complaints reported in the primary care setting. Although non-pharmacological treatments such as the CBT have been suggested to be useful in combating the persistent insomnia, the efficacy and clinical utility of CBT for primary insomnia have yet to be determined. METHOD: A systematic search of Ovid, MEDLINE, psychINFO, PsycARTICLES, CINAHL, and EMBASE databases of papers published between 1993 and 2004 was conducted, using the following medical subject headings or key words: insomnia, primary insomnia, psychophysiological insomnia, sleep maintenance disorders, sleep initiation disorders, non-pharmacological treatment, and cognitive behavioural therapy. A total of seven papers was included in the review. FINDINGS: Stimulus control, sleep restriction, sleep hygiene education and cognitive restructuring were the main treatment components. Interventions were provided by psychiatrists except for one study, in which the CBT was delivered by nurses. Among beneficial outcomes, improvement of sleep efficacy, sleep onset latency and wake after sleep onset were the most frequently reported. In addition, participants significantly reduced sleep medication use. Some studies gave follow-up data which indicated that the CBT produced durable clinical changes in total sleep time and night-time wakefulness. CONCLUSIONS: These randomized controlled trial studies demonstrated that CBT was superior to any single-component treatment such as stimulus control, relaxation training, educational programmes, or other control conditions. However, heterogeneity in patient assessment, CBT protocols, and outcome indicators made determination of the relative efficacy and clinical utility of the therapy difficult. Therefore, the standard components of CBT need to be clearly defined. In addition, a comprehensive assessment of patients is essential for future studies.