The thermodilution method of measuring cardiac output has a firm scientific basis and provides data to assist clinicians in assessing the hemodynamic function of patients and evaluating therapeutic interventions. Most of the research that validated this method of measurement was conducted from 1954 to 1979. Research in the 1980s focuses primarily on refining measurement techniques evaluating protocols that will simplify measurements in the clinical setting, and testing new devices that have the potential for affecting the accuracy of measurements. Although discrepancies between theory and application took years to resolve resulting in initial resistance to this method, thermodilution cardiac output measurement is now well accepted by researchers and clinicians as safe, simple, and accurate.