This investigation was aimed to study the effect of contrast media on the cardiovascular system. So in thisstudy, pithed rats were used whether alteration in cardiovascular system by contrast media were controlledcentrally. Furthermore, several hypertonic solutions were also used to clarify the effect of contrast media. Theresults are as follows: 1. Intravenous injection of contrast media in rats(2.5m/kg) caused hypotension andbradycardia. The effects were neither blocked by pretreatment of atropine nor pyribenzamine+atropine. 2. NaCl4.7%, dextrose 24.8%, urea 9.0% and glycerol 10.1%(v/v) which were equiosmolar with contrast media, causedhypotension, but did not affect the heart rate. 3. In pithed rats, intravenous injection of Angiografin increasedblood pressure in a dose-dependant manner, and caused decrease in heart rate compared with those of control rats. 4. In pithed rats, bradycardia by intravascular injection with Angiografin was partialy blocked by atropine. 5.Metrizamide of which iodine content was adjusted to 280 mg/ml caused increased in blood pressure when was injectedintravenously in pithed rats with little effect on heart rate. 6. When perfused with contrast media in rathindlimb at 15ml/kg speed both perfusion pressure and flow effluent incereased, simultaneously. These resultssuggest that hypotension might be caused by the central effect due to hyperosmolarity of contrast media andbrachycardia caused by both parasympathetic stimulation and direct inhibitory action on the cardiac conductivesystem.