Background: Early Warning Scores alert staff to preventable deterioration. Raised scores should lead to escalation of care. Aims: To establish response of staff to patients scoring National Early Warning Score (NEWS) of six or above and to identify patient and environmental factors affecting escalation by nursing staff. Methods: Service evaluation with prospective review of patient records of 118 beds on four medical wards during 20 night-shifts. Results: During 2360 observed bed days 109 patients triggered NEWS >=6 at least once during the observation period. Nursing staff escalated only 18 (17%) of these patients; nearly all of them had predefined chronic health conditions, the majority fulfilled criteria for frailty. Despite their higher 30-day mortality patients with COPD had lower escalation rates. Additionally wards that had more patients with a NEWS >=6 had lower escalation rates. Conclusion: Alarm fatigue and clinical judgement of staff might result in deviation from escalation protocols.