Apheresis is a procedure in which a specific blood component is selectively removed from a patient using computerized machines. In Canada it is currently used to treat over 30 different diseases, and, in 2002 a total of 8600 plasma exchange procedures were performed at a cost of over $7 million CDN. The Canadian Apheresis Group (CAG) is a national, volunteer organization of physicians and nurses who have special interest in evaluating the appropriate application of therapeutic apheresis (TA). It was formed in 1980 under the auspices of the Department of National Health and Welfare with the goals of providing a forum for the exchange of information among apheresis practitioners in Canada and developing statistically sound, prospective clinical trials to test the efficacy of plasma exchange as treatment for various disorders. The group includes representatives from each of the major medical centres in Canada so that there is a liaison between the CAG and local medical communities across the country. Over the years the group has been funded by Health Canada, then the Canadian Blood Committee, the Canadian Blood Agency and, for the past 3 years, by the Canadian Blood Services and the Province of Quebec. The CAG was the first group to organize a national database and, since 1981, has collected data from 42 apheresis units throughout Canada and more than 140,000 plasma exchange procedures. In 1981 there were 4716 plasma exchanges done while in 2002 there were 8561. This total has been relatively stable at approximately 8500 for each of the last 4 years. However, 20 years ago exchanges for hematological and neurological disorders each constituted 30% of the total and 15 years ago the majority of procedures were performed for neurological disorders (50%). In 2002 the majority of procedures were performed for hematological disorders (55%) and neurological disorders had fallen to 40% of the total. We believe these changes have been of a controlled and appropriate nature as a result of the activities of the CAG. We have developed national practice guidelines and have directed studies in a number of diseases, the results of which have refined practice across the country. We have also monitored replacement fluids and have had a significant effect on the appropriate use of plasma or albumin. Over the past 22 years, the activities of the CAG have lead to a rational, cost effective, use of TA in our country, have promoted the dissemination of knowledge among apheresis practitioners and have fostered optimal patient care.