This book is the result of the HIV / AIDS symposium which was held in Brussels, Belgium, on October 17-19, 1985. The first cases of AIDS were described in mid-1981 in homosexual men and drug abusers where an unusual combination of opportunistic infections and neoplasms were observed. Early 1984, the European Parliament, alerted by the ever increasing number of cases reported in the United States and Europe, voted a resolution recommending an emergency Community program. This was followed by the creation of the EC Working Group AIDS made of physicians both from basic and clinical science. A number of meetings were held in the last two years in order to implement a coordinating action in the field of immunology, virology, epidemiology, and lastly clinical aspects.