Abstract: The present invention relates to an improved apparatus and method for measuring blood pressure. Both include a first sensor for detecting an instantaneous pulse rate, an inflatable cuff, and a second sensor to monitoring the pressure within the cuff. The cuff sensor adapted to detect oscillometric complexes associated with a patient's pulse. Both the apparatus and the method provide for detecting arrhythmia from the patient's instantaneous pulse rate. A characteristic of the oscillometric complexes is measured, and match determination means provided for determining whether at least two adjacent oscillometric complexes are equivalent. A first set matching criteria are used under normal conditions. A second set of matching criteria are used when arrhythmia are detected. A controller is provided for controlling the pressure within the cuff. At the outset of a blood pressure measurement the cuff is inflated to a pressure greater than the patient's systolic pressure.