Plasma exchange: a selective form of blood-letting

The technique of, and indications for, plasma exchange are presented. This selective form of plasma removal has re-established "blood-letting" in medical therapeutics on a scientific basis. It is the most appropriate therapy when hyperviscosity or haemostatic failure complicate immunoproliferative disease. Plasma exchange is also a significant advance in the management of fulminant forms of autoimmune disease, but in many other conditions it must be regarded as experimental.