BACKGROUND: Heart failure with systolic dysfunction occurs frequently. Studies in North America and Germany have shown a high prevalence of sleep-disordered breathing in patients with heart failure. AIMS: To assess the prevalence of sleep-disordered breathing and its associated risk factors in French patients with heart failure. METHODS: A total of 316patients with stable heart failure and a left ventricular ejection fraction less or equal to 45% underwent polygraphy prospectively to diagnose sleep apnoea syndrome, defined as an apnoea-hypopnoea index greater or equal to 10events/h. RESULTS: Mean age, left ventricular ejection fraction, and body mass index were 59+/-13years, 30+/-11% and 28+/-6kg/m(2), respectively. The prevalence of sleep breathing disorder was 81% (n=256); 30% of syndromes were classified as central and 70% as obstructive. The mean apnoea-hypopnoea index was high (30+/-3events/h) and a large proportion (41%) of syndromes had an apnoea-hypopnoea index greater or equal to 30events/h. A central sleep apnoea syndrome pattern was associated with more severe heart failure and a more elevated apnoea-hypopnoea index than an obstructive pattern. The prevalence of sleep-disordered breathing was lower in women than in men (64% versus 85%; chi(2)=0.0003) as was its severity (mean apnoea-hypopnoea index 15+/-13events/h versus 27+/-19events/h, p=0.0001). CONCLUSION: The prevalence of sleep-disordered breathing was high in a French heart failure population, with most syndromes having an obstructive pattern. Prevalence and severity were higher in men than in women.