1. Plasma concentrations of human calcitonin were measured in groups of patients with chronic renal failure, treated either conservatively or by haemodialysis, and compared with a normal group of persons.
2. Plasma calcitonin was statistically significantly elevated in both groups with renal failure.
3. When the data from the three groups were pooled, plasma calcitonin was found to be inversely correlated with total calcium and directly correlated with plasma creatinine.