Halopropane is a noninflammable volatile liquid which has been found to possess properties of general anesthesia. Experiences in animals and in man have indicated that the drug is capable of producing adequate surgical relaxation and reasonably prompt induction and recovery. Experimental studies in the laboratory with dogs have indicated that it sensitizes the heart to the intravenous injection of epinephrine in a manner similar to halothane and cyclopropane. Eighty-two patients undergoing various surgical procedures were studied. Adequate operating conditions were obtained in all. However, the incidence of arrhythmias was sufficiently great that the drug was considered not completely satisfactory for clinical anesthesia in man. The uptake and excretion of halopropane from the blood was examined in 10 patients, and it was found that the blood level fell slowly, suggesting that the drug is highly soluble in fat. Because of the number of cardiac arrhythmias, some very severe, seen in these patients, it is concluded at this time that the drug probably is not a useful anesthetic agent.