Background: Central periodic breathing (CPB) is common following acute stroke, but its prognostic significance is uncertain. We determined the frequency of CPB on admission with stroke and assessed whether it was related to outcome. Methods: We measured arterial oxygen saturation (SaO(2)), chest wall movements and nasal airflow continually with portable monitoring equipment in a large cohort of acute stroke patients, from arrival at hospital through acute assessment to reaching the ward. Baseline neurological examination and 3-month outcome (modified Rankin scale, MRS) were assessed blind to recordings. CPB was defined as cyclical rises and falls in ventilation, with intermittent reduced respiratory airflow or total apnoea. Results: CPB was common in acute stroke (33/138, 24%), but was poorly recognised by clinical staff. Patients with CPB were more likely to have a total anterior circulation syndrome and higher National Institutes of Health Stroke Scale scores than those without (both p < 0.01). Patients with CPB had significantly higher median SaO(2) than those without (p < 0.01), unrelated to whether they received oxygen or not. At 3-month follow-up: 91% of patients with CPB were dead or dependent (MRS >= 3) compared with 53% of those without ( OR 8.8; 95% CI 2.5 – 30.5); the association remained statistically significant after adjusting for covariates (OR 5.9; 95% CI 1.4 – 25.4). Conclusion: CPB is independently associated with poor outcome after stroke, but is not by association with hypoxia. Further work is required to identify causes, effects and interventions that might improve effects of CPB. Copyright (c) 2006 S. Karger AG, Basel.