Autonomic function in patients with uraemia treated conservatively, by haemodialysis, and by transplantation was evaluated by the pupillary reaction to tyramine, the Valsalva manoeuvre and a postural tolerance test. The pupillary reaction to tyramine is diminished in haemodialysis patients compared with control subjects. Renal transplantation improves, but does not correct the pupillary reaction to tyramine. The frequency of the diminished response roughly correlates with the degree of renal insufficiency, with results of a Valsalva manoeuvre, and with postural tolerance tests. Our data show that uraemic autonomic dysfunction is improved by successful renal transplantation, but not by adequate haemodialysis.