Chronic heart failure (HF) is a prevalent clinical syndrome in which both central and obstructive sleep disordered breathing (SDB) have been described. The aim of this research was to investigate the mechanisms causing central SDB, their consequences with reference to sleep and physical activity, and the way in which treatment modalities may modify these. The first study of this thesis is the SERVE-HF study, a randomised controlled trial of adaptive servoventilation (ASV) to treat central SDB in patients with CHF. This study is ongoing and aims to test the hypothesis that patients randomised to ASV will have a reduction in mortality compared to controls. Data regarding those randomised at the Royal Brompton Hospital are presented alongside data on ventilator compliance in the ASV group. The second study investigated ventilatory control, in HF patients both with and without SDB. It tested the hypothesis that those with central SDB had heightened chemosensitivity (assessed by the hypercapnic ventilatory response, HCVR) compared to those with no SDB and older healthy controls. The third study explored the effect of treatment on ventilatory control by testing the hypothesis that the implantation of a cardiac-resynchronisation therapy pacemaker would be associated with a reduction in the HCVR from baseline to 3 months post implantation. The fourth study investigated the consequences of SDB in CHF. Physical activity, subjective sleepiness and sleep were assessed in patients with CHF and older healthy controls to test the hypothesis that physical activity would be reduced in those with central SDB compared to those without SDB, and reduced in both patient groups compared to the controls. In summary, this thesis investigated the mechanisms underlying central SDB in patients with HF, to elucidate their consequences, both by day and night and to address the ways in which treatment modalities may modify these pathophysiological mechanisms. [For supplementary files please contact author].