The effect of secondary HPT [hyperparathyroidism] on PMN [polymorphonucleocyte] function, as assessed by CL [chemiluminescence], was studied in 2 groups of patients. Group 1 comprised 7 patients with no clinical evidence of secondary HPT and mildly elevated levels of serum iPTH [immunoreactive parathyroid hormone] (mean 2.7 .+-. 0.9 .mu.leq/ml), and group 2 had 6 patients with clinical and radiological evidence of secondary HPT and higher (P < 0.001) levels of iPTH (mean 26 .+-. 7 .mu.leq/ml). PMN from group 2 patients demonstrated 68% .+-. 9 augmented CL in the presence of autologous serum. Cross-incubation studies showed that sera from group 2 patients induced augmented CL in normal PMN. PMN from group 2 patients showed induced CL in the presence of normal serum. The augmenting effect of group 2 sera did not correlate with the level of Ca, P, creatinine or blood urea nitrogen in serum. After successful subtotal parathyroidectomy, evident by the decrease of serum iPTH levels, the CL of group 2 PMN and the ability of group 2 sera to induce augmented CL in normal PMN decreased (P < 0.025). Secondary HPT may be directly or indirectly responsible for the altered leukocyte function in some patients with uremia, particularly those with marked elevation of iPTH.