During cardiopulmonary resuscitation in 12 patients, Doppler ultrasound monitoring of radial arterial flow provided an audible, instantaneous flow sound to which the resuscitation team referred, along with the monitor electrocardiogram (EKG), in determining hemodynamic status. Incidental to the resuscitation effort, a separate analog flow signal and the monitor EKG were simultaneously recorded in eight patients. Doppler blood flow monitoring allowed evaluation of effectiveness of cardiac massage; immediate recognition of electromechanical dissociation; rapid determinations of blood pressure, often during profound hypotension, and estimates of changes in cardiac output. When the hemodynamic consequences were immediately obvious, both ineffective chest compression and pauses longer than five seconds during effective chest compression were not tolerated by those in attendance, for whom the Doppler flow signal often became the primary reference in determining the patient's cardiac status.