In the present study we investigated the relationship between secondary hyperparathyroidism in renal graft recipients and post-transplantation acute tubular necrosis (ATN). Patients were divided into two groups according to graft function: group A consisted of 28 patients who had an uneventful postoperative period and did not require haemodialysis. Group B comprised 26 patients with primary non-function of the graft due to biopsy-proven ATN who required continued haemodialysis for the first postoperative week or longer (mean 14.2 +/- 8.7 days). Both groups had comparable donor characteristics, HLA-matching and ischaemia times. All patients were given cyclosporin and low-dose prednisolone for immunosuppression. Pretransplant levels of intact PTH were significantly greater in group B than in group A (203.5 +/- 193.1 pg/ml versus 81.7 +/- 45.2 pg/ml, P < 0.01). Group B patients had more transplant biopsies (50 versus 7) and a longer hospitalization time (33.4 +/- 10.9 days versus 21.9 +/- 11.9 days, P < 0.01), although serum creatinine on the day of discharge was higher in group B (1.77 +/- 0.51 mg/dl versus 1.5 +/- 0.45 mg/dl, P < 0.05). We conclude that patients with secondary hyperparathyroidism as assessed by measuring circulating levels of intact PTH have an increased incidence of ATN.