In this paper the development of objective criteria for data reduction, parameter estimations and phenomenological description of arterial pressure pulses are presented. The additional challenge of distinguishing between the cyclical and incoherent contributions to the wave form is also considered. By applying the technique of phase averaging to a series of heart beats, a characteristic pulse was determined. It was shown that the beats from a paced heart are very similar and while beats from an unpaced heart will vary significantly in time and amplitude. The appropriate choice of a reference point is critical in generating phase averages that embody the characteristic behaviour