Computer analysis of blood pressure and heart rate fluctuations and the quantification of their interaction in the time (sequence method) or in the frequency domain (spectral analysis) offer a dynamic evaluation of the sensitivity of baroreflex control of the heart (BRS) in daily life conditions. Use of these techniques in the analysis of 24 hour intra-arterial blood pressure and heart rate recordings has shown that in real life BRS is continuously modulated over time and is characterized by a pronounced increase at night as compared to the daytime. In a number of pathophysiological states (hypertension, aging and autonomic failure), average 24 hour BRS is markedly lower than in normal subjects and its day-night modulation is blunted to a variable extent. These time domain and frequency domain techniques provide generally superimposable results and represent unique tools not only to quantify differences in BRS between different steady-state conditions, but also to track fast changes in BRS induced by behavioural stimuli on a minute-to- minute basis. They offer a deeper insight into daily life cardiovascular regulation in normal and diseased conditions with no need of external interventions.