Byeong-hun An showed all his Olympic pedigree as he took a share of the lead in the early stages of golf's return to the Games for the first time in 112 years.
Local favourite Adilson da Silva had the honour of hitting the opening tee-shot at the Olympic Men's Golf Competition on Thursday morning but it was his playing partners who made the biggest impression as both An and Canada's Graham DeLaet reached four under at the turn.
Australian Marcus Fraser was also in a share of the lead after six holes, with Thomas Pieters just a further shot back.
An has some serious Olympic pedigree with both his parents having won medals in table tennis at the 1988 Seoul Games.
The South Korean had the dubious honour of making the first bogey of golf's return with a three-putt on the first but he followed it with the first birdie from 15 feet on the second.
A close approach on the next led to another birdie and when he also made gains on the eighth and ninth, he was in a share of the lead.
DeLaet was looking to make it back-to-back wins for Canada - albeit 112 years apart - after George Lyon's triumph in 1904, and he had birdies on the third, fifth, sixth and eighth.
Fraser took advantage of the par five first and, after a bogey on the next, went on a stunning run of four birdies.
An approach to four feet and excellent tee-shot set up gains on the third and fourth before the putter got hot as the Maybank Championship Malaysia winner holed from 23 and 25 feet on the fifth and sixth.
Big-hitting Belgian Pieters was using his length to his advantage as he too birdied the first and then drove the par four third to set up another birdie before holing a 17-footer on the sixth.
France's Julien Quesne, Portugal's José-Filipe Lima and South African Brandon Stone were then in the group at two under, a shot clear of Belgian Nicolas Colsaerts, Germany's Martin Kaymer and South Korea's Jeunghun Wang.
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