This study was undertaken to evaluate the diagnostic accuracy and time required by first responders to assess the carotid pulse in potentially pulseless patients. We conducted a prospective, randomized study of first responders (n = 206; four different training levels) and were blinded as to the patients' conditions in the cardiac operating rooms of a university hospital. Sixteen patients underwent coronary artery bypass surgery on nonpulsatile cardiopulmonary bypasses. Carotid pulse check was performed either during pulsatile (spontaneous) or during nonpulsatile (extracorporeal) circulation. Patients' hemodynamic status at the time of assessment, diagnostic accuracy of the first responders, and the time required to diagnose carotid pulsatility or pulselessness were documented. Within 10 secs, only 16.5% of the participants (34 of 206) were able to reach any decision about their patients' pulse status. Assessments that were both rapid and correct (15%, i.e., 31 of 206) occurred almost exclusively in pulsatile patients. Advanced training level shortened the delay to decision and improved its accuracy. However, merely 2% of the participants (1 of 59) correctly recognized a truly pulseless patient within 10 secs. Recognition of pulselessness of the carotid artery by rescuers with basic cardiopulmonary resuscitation training is time-consuming and highly inaccurate. Although the carotid pulse check needs to be taught, its importance in the context of layperson basic life support should be de-emphasized.