A new approach was developed to analyse the relationships between cardiovascular parameters using the concept of Statistical dependence and a new coefficient, Z, that expresses the dependence between two Statistical events, was defined. Using blood pressure (BP) and heart rate (HR) beat-to-beat values recorded in rats, we showed in a previous study that some BP and HR couples of values were dependent due to the activity of the baroreflex. In this study, the ability of Z analysis to estimate baroreflex sensitivity (BRS), using mean BP (MAP) and HR values was tested. Dependent (MAP, HR) couples were selected with Z coefficient and a linear regression was performed between these selected MAP and HR values. The regression slope, taken as the index of BRS, was strongly correlated to BRS estimated with a pharmacological method. In humans, using Finapres^® BP recordings, BRS was estimated from systolic BP and HR values with the Z method and with spectral analysis, by Computing the average modulus gain in the 0.07 – 0.14 Hz band. The Z method exhibited a good reproducibility and results obtained with the two methods were significantly correlated. In conclusion, Z coefficient allowed to isolate some couples of BP and HR values related to baroreflex activity. In rats and in humans, it appears able to provide a new estimate of the spontaneous BRS using Z coefficient as a selective filter.