Real-time hemodynamic monitoring provides useful information that can be used to assess and optimize mechanical and pharmacological interventions during CPR. The standard algorithms should always be the initial approach to resuscitation, because they offer a rapid, logical, coordinated series of treatments with proven success. Pressure and flow measurements during conventional, closed-chest CPR in humans indicate that the technique typically produces a hemodynamic state resembling profound cardiogenic shock, with a low systemic arterial pressure, markedly reduced cardiac output, and high intravascular filling pressures. End-tidal carbon dioxide monitoring provides useful, noninvasive information during clinical resuscitation. A low end-tidal carbon dioxide value during resuscitation should alert the rescuers that something is wrong with ventilation, perfusion, and/or carbon dioxide production and should prompt a search for correctable causes. If one or more hemodynamic parameters are being monitored at the time the patient develops cardiac arrest (eg, an intensive care unit patient who has an arterial line and a pulmonary artery catheter in place), it is appropriate for the resuscitation team to pay attention to the data that are generated during the resuscitation, particularly if the initial algorithm approach is not successful. For patients who are not being monitored at the time of their arrest, end-tidal carbon dioxide measurements provide noninvasive, semiquantitative information that can help the team detect and troubleshoot problems during resuscitation. Further research and better, more affordable technologies are needed to provide in- and out-of-hospital resuscitation teams feedback on the hemodynamic effectiveness of their resuscitative efforts.