BACKGROUND Clodronate is a bisphosphonate used in the treatment of hypercalcaemia of various aetiologies. The major route of elimination of clodronate is renal excretion. The aim of the study was to derive data for the adjustment of dosage in haemodialysis patients. METHODS The pharmacokinetic parameters describing the fate of an intravenous infusion of 300 mg clodronate disodium were studied in 10 haemodialysis patients. Clodronate disodium in serum, urine and dialysate samples was analysed by capillary gas chromatography with mass-selective detection. RESULTS Of the 300 mg clodronate infused, 159 mg (53%) was excreted into dialysate within 4 h. Clearance by haemodialysis (CLD) was 87.8+/-16.2 ml/min, accounting for 84% of total serum clearance (CLtot). Non-renal, non-dialysis clearance (CL(NRD)) represents the removal of the drug via other routes than dialysis or kidneys. The greatest CL(NRD) was observed in patients with most severe hyperparathyroidism. There was a positive correlation between CL(NRD) and plasma intact PTH concentration. CONCLUSIONS According to the present findings, standard haemodialysis removes clodronate effectively from the circulation, and total clearance in haemodialysis patients on a dialysis day is not very different from that in healthy subjects. The regimen of dosing intravenous clodronate in hypercalcaemia can also be used in haemodialysis patients. The portion of clodronate eliminated by routes other than via dialysate or kidneys, i.e. predominantly via skeletal deposition, was related to the severity of hyperparathyroidism.