OBJECTIVES: Cervical dystonia is a disabling, painful condition involving involuntary movement and posturing of the head and neck. Botulinum toxin injections are the standard of care in the symptomatic management of this condition, but need to be re-administered regularly to maintain a stable improvement. The duration of clinical effect and thus, frequency of need for reinjection may be dependent on the product used and can impact annualized drug and health care utilization costs. METHODS: A literature search was undertaken to identify prospective or retrospective studies reporting duration of effect of onabotulinumtoxinA (BOTOX®). A formal meta-analysis was conducted using Comprehensive Meta-Analysis Version 2.  Both a fixed effects and random effects model were performed.  The quality of each identified journal article was evaluated using the Cho & Bero Quality scoring instrument by two separate investigators.  Differences in scores were resolved through conference.  Subgroup analyses were performed on several moderating variables including study quality and dose of onabotulinumtoxinA.  RESULTS: Of the identified potential journal articles, 13 studies met the inclusion criteria and were used for the meta-analysis.  The duration of effect of onabotulinumtoxinA in cervical dystonia was found to be 13.7 weeks (95% CI 13.4 – 13.9 weeks) for the fixed effects model and 13.5 weeks (95% CI 12.7 – 14.3 weeks) for the random effects model.  A meta-regression found that the higher the quality score, the shorter the duration of effect.  Another meta-regression found that doses of onabotulinumtoxinA greater than 200U generally resulted in a longer duration of effect than doses below 200U.  CONCLUSIONS: Based on the published literature, the duration of effect of onabotulinumtoxinA was 13-14 weeks. This suggests that, in general, patients with cervical dystonia treated with onabotulinumtoxinA should require approximately 4 treatments per year. A dose-effect for duration was also identified.