Superb results from the outset quickly attracted the attention of the ambitious Tecno company from Italy, who signed him in 1968. With them, he won the 1969 Formula Three Championship.

Peterson made his Grand Prix debut in a March 701 for Colin Crabbe’s works-supported Antique Automobiles Racing Team at the 1970 Monaco Grand Prix. The limited budget of Crabbe’s privateer team allowed only minimal testing, and Peterson qualified 12th out of 16 cars in the race. He was 10 places behind Jackie Stewart and Chris Amon, both on the front row of the grid in their newer specification 701s, but only just behind the more experienced Jo Siffert in the second works March. Peterson was the only March driver to finish the race, in seventh place. In 1971 Peterson moved up to the full March works team, and made an instant impression. Five Formula One Grand Prix second places earned him the position of runner-up to Jackie Stewart in that year’s World Championship. Within that year, Peterson drove in the World Sports Car Championship driving an Autodelta Alfa Romeo to win the Watkins Glen 6 hours. Peterson stayed at March until 1973, when he signed for John Player Team Lotus to partner Emerson Fittipaldi.

For 1974, the Lotus 76 was brought forth. The car, however, proved to be a failure, disliked by both Peterson and his teammate Ickx. The team therefore opted to let them drive the much older Lotus 72:s. Peterson did well in the old car and claimed three more victories: the French and Italian Grands Prix, as well as the Monaco Grand Prix.

He also continued to drive sports cars, particularly for BMW in 1974 and 1975. For instance, he was paired with Hans-Joachim Stuck in a BMW 3.0 CSL for the South African “Wynn’s 1000” in November 1975, where they started on pole but finished in second after a number of stops with engine vibrations, spark plug, and similar problems. Stuck and Peterson together for BMW in Europe, Africa, and also in North America.

1975 was a bad year for Lotus. Peterson and Ickx were forced to drive with the now archaic 72 model, whose age was now really beginning to show.

In 1977, he raced for Tyrrell, driving the six-wheel Tyrrell P34B. Peterson retired from the opening four races of 1977, he spun off in Argentina, was involved in a crash with Jochen Mass’s McLaren and Clay Regazzoni’s Ensign in Brazil, and suffered fuel systems problems in South Africa and United States West. He finished eight in Spain but retired at Monaco with brake failure. Peterson’s only podium finish was a third place at a rain-affected race in Belgium. Hopes were high at home in Sweden but Peterson retired with ignition problems and then finished 12th at France. He had an engine failure in Britain, finished ninth at Germany and got fifth in Austria. Peterson retired with ignition problems at Holland, sixth in Italy and 16th in the United States. Peterson retired from the last two races of 1977, a fuel leak in Canada and in Japan, he collided with Gilles Villeneuve’s Ferrari but the crash killed a marshal and photographer as they were standing in a prohibited area of the track when the accident occurred.

The 1978 Italian Grand Prix at Monza started badly for Peterson. In practice he damaged his Lotus 79 race car beyond immediate repair and bruised his legs in the process. Team Lotus had a spare 79, but it had been built for Andretti, and the taller Peterson did not fit comfortably inside. The team’s only other car was a type 78, the previous year’s car, which had been dragged around the F1 circuit that season with minimal maintenance.

At the hospital, Peterson’s X-rays showed he had about 27 fractures in his legs and feet. After discussion with him, Peterson was sent to intensive care so that the surgeons could operate to stabilize the bones. There was some level of dispute between the doctors regarding whether all fractures should be immediately fixed or not. During the night, Peterson’s condition worsened, and he was diagnosed with fat embolism. By morning he was in full kidney failure due to the embolism, and was declared dead at 9:55 am on 11 September 1978.

His teammate Mario Andretti clinched the championship at the race. “It was so unfair to have a tragedy connected with probably what should have been the happiest day of my career”, Andretti said, “I couldn’t celebrate, but also, I knew that trophy would be with me forever. And I knew also that Ronnie would have been happy for me”. Peterson took second place in the 1978 drivers’ standings posthumously.

In 1979, George Harrison paid tribute to Peterson with a song and music video called “Faster”.

The circumstances of Peterson’s death were prosecuted in an Italian criminal court. Driver Riccardo Patrese and race director Gianni Restilli were both charged with roles; Patrese, for manslaughter because of an unsafe maneuver on track which was considered to be a primary cause of the wreck, and Restilli, as contributing to Peterson’s death by starting the race with a premature start signal. Both were cleared of criminal charges on 28 October 1981.

Peterson’s widow Barbro (née Edwardsson) never got over his death and committed suicide on 19 December 1987. She was buried alongside Ronnie in the Peterson family grave in Örebro. She and Ronnie had a daughter named Nina Louise (named after Jochen Rindt’s wife) who was born in November 1975.

There is a statue of Peterson in Örebro (59°15′43″N 15°14′17″E / 59.26193°N 15.23812°E / 59.26193; 15.23812) by Richard Brixel. The official Ronnie Peterson museum was officially opened by Ronnie’s daughter, Nina Kennedy, in Örebro on 31 May 2008. The museum closed in October 2009 because it was unable to secure further government funding.

During the 2014 Monaco Grand Prix fellow Swedish racing driver Marcus Ericsson wore a special helmet in tribute to Peterson which was modeled on Peterson’s.

In 2016, in an academic paper that reported a mathematical modeling study that assessed the relative influence of driver and machine, Peterson was ranked the 21st best Formula One driver of all time.