Sleep disordered breathing (SDB) has a high prevalence and prognostic impact in patients with chronic heart failure (CHF). Aim of this study was to investigate variability of SDB parameters in patients with stable CHF. Cardiorespiratory polygraphy was used to determine SDB in two consecutive nights in 50 CHF patients (NYHA class > or = II, LV-EF < or = 40%). The apnea-hypopnea-index (AHI) and apnoea-index (AI) were used to quantify SDB severity. Central, obstructive or mixed SDB were classified according to the majority of events. There was an excellent correlation in AHI (r = 0.948, P < 0.001) and AI (r = 0.842, P < 0.001) results of both nights. The overall number of detected apnea and hypopnea during the first night as compared to the maximum of both nights was 85% for the AHI and 77% for the AI. The reproducibility was dependent on SDB severity: AHI 15-29/h = 87%, AHI > or = 30/h = 92% and AI > or = 10/h = 83%. Classification was identical in 17 out of 19 patients with AI > or = 10/h. In patients with stable CHF a single night of cardiorespiratory monitoring leads to representative results on severity and type of SDB. This may enhance the applicability and dissemination of cardiorespiratory polygraphy in clinical practice.