The 1978 Mason-Dixon 500 was a 500-lap NASCAR Winston Cup Series race held on May 21, 1978, at Dover Downs International Speedway in Delaware. A crowd of 36,013 fans watched a full 40-car field compete on the one-mile concrete oval.
Buddy Baker captured the pole position with a speed of 135.452 mph. The race was slowed by six cautions for 37 laps. David Pearson, driving the #21 Wood Brothers Mercury, staged a remarkable comeback after falling two laps behind at one point. He went on to win by 12 seconds over Cale Yarborough with an average speed of 114.664 mph. Lennie Pond finished third, followed by Benny Parsons in fourth and Neil Bonnett in fifth. Pearson earned $16,600 for the victory — his 101st career NASCAR win.
After the race, Benny Parsons left Dover as the points leader, holding a 36-point advantage over Dave Marcis.
