To test the validity of our impression that in the absence of objective clinical evidence of nerve-root impingement there is a disproportionately high incidence of complications associated with myelography, the results in 248 patients were reviewed retrospectively and those in 110 were studied prospectively. Of all 358 patients, 53 per cent had complications after myelography with injection of metrizamide, of which headache and nausea and vomiting were the most frequent. The incidence of complications in the 112 patients whose objective clinical and myelographic findings were consistent was compared with that in the 180 patients who had only subjective complaints and normal myelographic findings. The incidence of complications was 30 per cent in the former group and 70 per cent in the latter group, an almost twofold difference (p greater than 0.05). The 110 patients in the prospective study were asked to grade the intensity of their headache after myelography. Of the thirty-one patients with positive objective clinical and myelographic findings, ten complained of headache, which was mild in seven (70 per cent) and severe in three. Of the sixty patients with only subjective complaints, thirty-eight complained of headache, which was mild in twelve (32 per cent) and severe in twenty-six.