The use of citrate as an anticoagulant in haemodialysis is for patients who are recognised to be at risk if systemically anticoagulated. This paper describes a trial of use of a technically simple procedure involving the use of small volumes of citrate solution. It introduces the measurement of plasma citrate levels in a population of stable patients on regular dialysis treatment. Using synchronous pre- and post-dialyser blood samples, measurement of the whole blood clotting times demonstrated the restriction of anticoagulation to the extracorporeal circulation. It is concluded that citrate anticoagulation is safe, acceptable and simple for use in haemodialysis for patients at risk from systemic anticoagulation.