The FIA introduced Group B in 1982 as part of a restructuring of its Appendix J production car categories. Group N and Group A replaced the outgoing Group 1 and Group 2 for standard and modified touring cars, while Group B combined and replaced Groups 3, 4, and 5, covering grand touring cars with a minimum of two seats. The defining characteristic of Group B, and the foundation of its outsized influence, was the extremely low homologation requirement: manufacturers needed to produce only 200 cars to qualify a vehicle for competition, compared to 5,000 for Groups N and A. Evolution variants required only 20 additional units.
This threshold opened the door to purpose-built competition machines with minimal road car equivalents. Manufacturers could use space frame chassis, exotic materials, and configurations impossible in mass-production vehicles. The rules placed almost no restrictions on technology, design, or materials, with weight and engine displacement the primary control mechanism.
Engine displacement classes used a 1.4 equivalence factor for turbocharged engines. Key classes included the 3,000 cc category at a 960 kg minimum weight, used by the Audi Quattro and Lancia 037, and the 2,500 cc class at 890 kg, used by the Peugeot 205 T16 and Lancia Delta S4. Power outputs climbed from around 250 hp in 1981 to more than 500 hp in the leading cars by 1986, as engineers learned to extract extraordinary power from turbocharging without any boost restrictions.
Group B cars began appearing from the first round of the 1982 WRC season at Monte Carlo, but no Group B car reached the podium that year. Audi carried Hannu Mikkola to the drivers' title in 1983 with the Quattro, which was still fundamentally a Group 4 machine. Lancia won the manufacturers' title with the rear-wheel drive 037, the last rear-wheel drive car to take the WRC manufacturers' championship. Opel and Toyota also entered Group B cars based on the Manta 400 and Celica respectively, finding success in national championships while struggling at WRC level.
Audi won both the manufacturers' and drivers' titles in 1984, with Stig Blomqvist taking the drivers' crown. Peugeot entered mid-season with the 205 T16, a mid-engined, four-wheel drive car operated under the supervision of Jean Todt with Ari Vatanen as lead driver. Peugeot dominated 1985, with Timo Salonen winning five rallies to claim the drivers' title. Vatanen was seriously injured in a crash in Argentina when his seat mounts failed.
Late in 1985, several significant new cars debuted. Lancia replaced the 037 with the Delta S4, a car using both a turbocharger and a supercharger for continuous power across the rev range. Ford entered with the RS200 and the Sierra RS Cosworth, Citroën with the BX 4TC, and Rover with the Metro 6R4.
The 1986 season began with enormous crowds drawn by the spectacle of Group B cars, but crowd control at many events was inadequate. In March, at the Rally de Portugal, Joaquim Santos crested a rise and turned to avoid spectators on the road, losing control of his Ford RS200. The car veered into another crowd, killing three people and injuring 31. All leading teams withdrew from the event. Ford team manager Peter Ashcroft confirmed he had already expressed concern over crowd control in WRC rallies.
In May at the Tour de Corse, Lancia's Henri Toivonen was leading the championship when, seven kilometres into the 18th stage, his Delta S4 flew off the edge of a corner and plunged down a wooded hillside. The car landed inverted, ruptured fuel tanks ignited by the turbocharger, and Toivonen and co-driver Sergio Cresto died. No witnesses saw the cause of the accident. Following these tragedies, the FIA banned Group B from the WRC effective 1987. Audi withdrew immediately after the Corsica round, stating the FIA decision took no measures to improve spectator safety.
The championship title that year also became controversial. Peugeot's cars were disqualified from the Rally Sanremo by Italian scrutineers, passing Lancia's Markku Alén to the provisional title. At the following RAC Rally, British scrutineers passed the same Peugeot cars as legal. FISA annulled the Sanremo result eleven days after the final round, transferring the title from Alén to Peugeot's Juha Kankkunen.
Group B regulations produced homologation specials that were among the rarest and most extreme road-legal machines of the twentieth century. Cars including the Audi Sport Quattro, Peugeot 205 T16, and Lancia Delta S4 remain benchmarks for performance within their category that have not been surpassed even decades later. The proposed successor, Group S, would have limited power to 300 hp with only ten cars required for homologation, but was cancelled alongside the Group B ban. That concept was eventually revived in 1997 as the World Rally Car specification.
Former Group B cars found a secondary life in European rallycross competition from 1987 through 1992, and in events such as the Pikes Peak International Hill Climb. The Porsche 959 and Peugeot 205 T16 both competed successfully in the Dakar Rally. The era is remembered simultaneously as a technical pinnacle and a safety failure, and carries the nickname "Killer B's" among those who focus on its dangers, while enthusiasts more broadly refer to it as the Golden Age of Rallying.