A new statistical method for expressing bonds between 2 variables is proposed, which 1) does not require any hypothesis and 2) may quantify a bond that varies over the ranges of variation of both variables. It allows to quantify the statistical dependence between 2 events with a coefficient, Z, using probabilities of each event and their conditional probability. When applied to blood pressure (BP) and heart rate (HR), the method gave the statistical dependence between 2 discrete values of the variables, expressed as amplitude intervals. Control rats, rats submitted to sinoaortic denervation (SAD) or to an early chronic sympathectomy (SNX) were included in a first study. BP was continuously recorded in baseline conditions during 24 hours in control rats and 30 minutes in SAD and SNX rats. The occurence frequency and the Z value were computed for each couple of systolic BP (SBP) and HR beat-to-beat values. Contour line representations of 3-dimensional Z histograms showed reproducible dependence zones in the (SBP, HR) plane. In control rats, dependence zones were found in the modal class and in 3 zones corresponding to 1) low SBP associated with high HR, 2) high SBP associated with high HR and 3) high SBP associated with low HR. Dependence zones 1 and 3 were not present in SAD rats and dependence zone 2 disappeared in SNX rats. These results suggest the participation of the baroreflex in the dependence between SBP and HR values located in zones 1 and 3 and of the sympathetic nervous system (SNS) in the dependence between SBP and HR values located in zone 2. A second study tested the ability of Z analysis to estimate baroreflex sensitivity (BRS), using mean BP (MAP) and HR values. Dependent (MAP, HR) couples located in zones 1 and 3 were selected and a linear regression was performed. The regression slope, taken as the index of BRS, was strongly correlated to BRS estimated with a pharmacological method. In conclusion, the concept of statistical dependence was applied to BP and HR values taken as statistical events. Z coefficient allowed to separate couples of BP and HR values related to baroreflex activity from those related to SNS activity. In addition, it allowed to estimate in a global manner the BRS from spontaneous BP recordings.