During the last 30 years in vivo blood cell separation, generally referred to apheresis, has established a central role in both blood donor programmes and therapeutics. The technological advances in apheresis equipment has made procedures safer, faster and more effective. This article will review the use of apheresis in clinical medicine with emphasis on plasma exchange and peripheral blood stem cell collection. Plasma exchange now has a pivotal role in the management of a range of disorders, specially those with autoimmune pathogenesis. However, Plasma exchange should be practised as one component of an integrated and frequently multidisciplinary approach to management. The harvesting of allogeneic or autologous of peripheral blood haemopoietic stem cells is increased and it has become the principle indication for apheresis in many haematology units. A well coordinated protocol approach to this procedure is important if adequate haemopoietic stems cells are to be collected and safely cyropreserved. This requires successful cooperation between medical, nursing and scientific personnel.