PURPOSE OF REVIEW: Critical illness is often preceded by physiological deterioration. Track and trigger systems are intended to facilitate the timely recognition of patients with potential or established critical illness outside critical care areas. The aim of this article is to review the evidence for the use of such systems. RECENT FINDINGS: Existing track and trigger systems have low sensitivity, low positive predictive values, and high specificity. They often fail to identify patients who need additional care and have not been shown to improve outcomes. The development of such systems must be based on robust methodological and statistical principles. At present, few track and trigger systems meet these standards. SUMMARY: Although track and trigger systems, combined with appropriate response algorithms, have the potential to improve the recognition and management of critical illness, further work is required to validate their utility. © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins.