For studying the hemodynamics of the greater and lesser circulatory system in animals, the impact of general anesthesia upon cardiovascular functions should be as small, as possible. The marked circulation-depressing effect of halothane, which has so far been given preference for experiments on large animals, was confirmed by the present study of the miniature pig. There was a significant decrease in MAP, cardiac index and dp/dt_max/IP, and an increase in PAP_p. Useful insights into hemodynamics, derived from experiments modeling the heart, lungs or vascular system cannot be gained for a cardiovascular system, the functions of which are greatly altered by such an anesthesia. As a new form of anesthesia with minimal cardiovascular influence, the ketamine-diazepam N₂O combination, which has already been successfully applied in operations on the open human heart, is introduced into experimental surgery.