Three hundred lumbar myelographies using a new water-soluble, non-electrolytic contrast medium, Amipaque, were assessed with reference to: 1) the correlation between radiological and operative diagnosis; 2) the side-effects during and after the myelography. Myelograms of the same reliability as those obtained with other water-soluble contrast media were obtained. However, arachnoiditis as sequelae to previous myelography with oil-soluble and earlier water-soluble contrast media prevented the correct evaluation in some cases. Spinal anaesthesia was not necessary. There was no case of muscle spasms or other serious complication. Eight patients who were re-examined with Amipaque more than two months later revealed no evidence of arachnoiditis as sequelae to the first Amipaque myelography.