Patients with acute myocardial infarction are frequently not fed hot and cold liquids because of possible deleterious effects on heart rate, blood pressure, and cardiac rhythm. In an attempt to identify and quantify such changes, hot liquid with a temperature in excess of 70°C and cold liquid at an average temperature of 7°C were ingested by 20 patients within 36 hours of documented myocardial infarction and by 11 control patients with severe anginal episodes or chest wall syndromes. Heart rate and rhythm were continuously monitored during ingestion of the hot and cold liquids, and blood pressure was recorded intermittently. No patient in either group had a change in cardiac rhythm or an increase in ectopy during ingestion of the hot or cold liquids. Changes in blood pressure and heart rate were also not significant during liquid ingestion by patients with infarction and control patients. The practice of avoiding ingestion of hot and cold liquids by patients with acute myocardial infarction is not supported by these observations.