Background/Aims: Severe secondary hyperparathyroidism is not infrequent in hemodialysis patients and recent studies suggest that parathyroid hormone (PTH) may play a role in the genesis of cell immunity abnormalities in uremia. The aim of the present study is to describe the effect of parathyroidectomy on T- and B-cell functions in hemodialysis patients. Methods: The study was performed on 6 patients with severe secondary hyperparathyroidism. iPTH, B, CD4<sup>+</sup>, CD8<sup>+</sup>, total number of lymphocytes, lymphoproliferative response to PHA, PWM and Candidin, and IgG, IgM, IL-2 production in vitro were determined 1 day before and 4 months after parathyroidectomy. Results: The lymphoproliferative response to PHA increased significantly after parathyroidectomy. We also observed a trend to an increase in production of IgG and IgM after PWM stimulation before therapy. Conclusion: The present study suggests that patients with extremely high levels of PTH show a complete restoration of impaired T-cell proliferation after parathyroidectomy.