It has been suggested, both by American, but particularly by British, surgeons that haemody-namic monitoring is unnecessary for adequate patient care. Without desiring to precipitate an international crisis, it is the opinion of the latter group that the American surgeons are “too slow” in the operating room. However, the record of the American cardiovascular surgeon speaks for itself, and speaks eloquently. Nevertheless, this writer had the opportunity recently to put the question to a distinguished panel of practicing anaethetists and surgeons, “If you had to abandon haemodynamic monitoring, how would this affect your practice?” All of the surgeons indicated that they would have to anticipate significant increases in both operative mortality and morbidity, in particular, of course, in the higher risk patients. It was their opinion that the magnitude of operation was not the primary determinant of risk, but more the ever-changing condition of the critical patient in the operating room. Thus, they would have to offer a less optimistic prognosis and decline operation in a greater proportion of patients because of the reduced likelihood of favourable outcome. The anaesthetists on the panel had similar viewpoints, related more to their inability to affect outcome in the operating room favourably. An increased morbidity and difficulties in post-operative care were also anticipated. As a generality, therefore, haemodynamic monitoring appears to have an important place in modern cardiovascular surgery. The complex patient with coronary disease and many of the patients with valvar heart disease alone, particularly when the patient is older and the lesions multiple, benefit from careful haemodynamic monitoring.