The diagnostic quality and side effects of Amipaque and Pantopaque as myelographic contrast agents were compared prospectively using the identical protocol in 167 cases (117 Amipaque, 50 Pantopaque). Good ratings were attained in 74% of Amipaque and 76% of Pantopaque examinations. Demonstration of nerve rootlets in the cauda equina and filling of lumbar root sleeves were superior with Amipaque. Amipaque more easily demonstrated the high posterior cervical subarachnoid space and the anterior and posterior margins of the cervical spinal cord. The incidence of postmyelographic headache was 38% with Amipaque and 32% with Pantopaque. Nausea and vomiting were more common with Amipaque. Two patients experienced grand mal seizures after examination with Amipaque.