Selective left vertebral angiography was carried out in 21 rabbits comparing the toxic effects of meglumine iothalamate (Conray meglumine), meglumine metrizoate (Isopaque Cerebral) and metrizamide (Amipaque). The iodine concentration for all 3 media was 280 mg/ml. General convulsions were seen in many of the animals with all 3 media. The convulsions occurred at higher doses and were milder with metrizamide than with the 2 other contrast agents. Bradycardia was also seen with all 3 media and there was no statistical significant difference between them in this respect. The mortality was approximately 50% with both meglumine iothalamate and meglumine metrizoate, while no animals died following angiography metrizamide.