Sequential changes in creatinine clearance (Ccr) were determined in 14 patients undergoing operation for phaeochromocytoma. All patients had been given alpha-adrenergic antagonists 2 weeks before surgery. In the younger group (mean age 40 +/- 2 years), Ccr improved following adrenal surgery. Urinary concentrations of epinephrine, norepinephrine and total catecholamines correlated inversely with Ccr. A similar inverse relationship was noted between tissue norepinephrine concentration expressed as microgram/g and Ccr to a lesser extent. In older patients (mean age 69 +/- 2 years) Ccr remained unchanged by this surgical procedure. No significant correlations were found between both parameters in the older group. It appears reasonable to presume that excessive amount of catecholamine plays an important role in the impairment of Ccr in relatively young patients with phaeochromocytoma, but other possibilities as regards the sequence of this phenomenon must be pursued in older patients.