Signals generated by biologic systems are characterized by a high degree of nonstationarities and noise. Phase-rectified signal averaging (PRSA) was shown to be superior to conventional methods in detection of periodicities in biologic signals. Bivariate phase-rectified signal averaging (BPRSA) is an extension of the PRSA-method for analysis of interrelationships between 2 synchronously recorded biologic signals. Here, we review the methodology of the technique and demonstrate its performance in simulated data. As application to biologic data, we use BPRSA to analyze synchronously recorded time series of systolic arterial blood pressure, RR intervals, and respiratory activity.