Tiger Woods made a flying start to his first Open in three years and Justin Thomas was also on the charge at Carnoustie.
A succession of back injury problems have prevented Woods from teeing it up at the third major of the season since St Andrews in 2015.
But the 14-time major champion drained a 12-footer at the opening hole and missed another lengthy opportunity at the second before nailing an approach at the fourth to within four feet for a second birdie to move to two under through four.
US PGA Championship holder Thomas was three under at the turn and a further gain at the 11th meant he was just one shot off clubhouse leader Kevin Kisner.
Tony Finau signed for a 67 and was in the clubhouse at four under alongside Erik van Rooyen and Zander Lombard.
Rory McIlroy, the 2014 victor, was one under par with five holes still to play, but world number one Dustin Johnson was struggling at two over at the same juncture.