Background: Healthy Outlook was a telephonic alert system for patients with Chronic Obstructive Pulmonary Disease (COPD) in the United Kingdom. It used routine meteorological and communicable disease reports to identify times of increased risk to health. We tested its effect on hospital use and mortality. Methods: Enrolees with a history of hospital admissions were linked to hospital administrative data. They were compared with control patients from local general practices, matched for demographic characteristics, health conditions, previous hospital use and predictive risk scores. We compared unplanned hospital admissions, admissions for COPD, outpatient attendances, planned admissions and mortality, over 12 months following enrolment. Results: Intervention and matched control groups appeared similar at baseline (n=1,413 in each group). Over the 12 months following enrolment, Healthy Outlook enrolees experienced more COPD admissions than matched controls (adjusted rate ratio 1.26, 95% CI, 1.05 to 1.52) and more outpatient attendances (adjusted rate ratio 1.08, 95% CI 1.03 to 1.12). Enrolees also had lower mortality rates over 12 months (adjusted odds ratio 0.61, 95% CI, 0.45 to 0.84). Conclusion: Healthy Outlook did not reduce admission rates, though mortality rates were lower. Findings for hospital utilisation were unlikely to have been affected by confounding.