Mario Andretti led throughout to record his second successive victory in the Spanish Grand Prix at Jarama, hosting its second race since the disastrous 1975 race at Montjuїc Park.
Andretti took pole in his revolutionary Lotus 78 and the opposition was reduced when Niki Lauda withdrew from the race after the warm-up session with severe back pain. It was discovered that he had run over a bump with sufficient force to fracture his seventh rib - one he had broken at the Nürburgring the year before.
Andretti led away and dominated the race but was chased in the early laps by Jacques Laffite until his Ligier developed a loose wheel and had to pit. That allowed Carlos Reutemann up to second with Jody Scheckter third, the Wolf once again a factor in its maiden season.
Although James Hunt was a retirement with engine failure, team-mate Jochen Mass kept out of trouble to finish fourth from the second Lotus of Gunnar Nilsson. The Brabham of Hans Stuck took sixth with Laffite seventh, poor reward after his early promise.
Andretti moved to second in the world championship, three points behind Scheckter. "All I wanted was fresh air in front of me," he said. "The car went like a clock; I was not even pushing it hard."