The Group B referred to a set of regulations introduced in 1982 for competition vehicles in sportscar racing and rallying regulated by the FIA. The Group B regulations fostered some of the quickest, most powerful and sophisticated rally cars ever built. However, a series of major accidents, some fatal, were blamed on their outright speed. After the death of Henri Toivonen and his co-driver in the 1986 Tour de Corse, the FIA disestablished the class, which was replaced as the top-line formula by Group A. The short-lived Group B era has acquired legendary status among rally fans,,,,
(from Wiki)