American Chris DiMarco clearly relished his US Masters debut by setting the early clubhouse target of seven-under par 65 for the rest of the field to chase.
DiMarco made his move early in the round with a run of three birdies from the fifth before reaching the turn in four-under 32 with another birdie at the ninth.
Even more impressive was the manner in which the 32-year-old handled 'Amen Corner'. He recorded birdies on the notoriously difficult 12th and 13th before adding another at the par five 15th.
James O'Driscoll is in second having completed the front nine in an impressive four-under par 32. The US amateur runner-up remains three behind through 13.
Ireland's Padraig Harrington made a blistering start of his own with birdies on the opening two holes, then immediately surrendered his position with bogeys at the third and fourth.
After a turbulent opening, Harrington was able to restore some stability to his round with a third birdie at the fifth, followed by a run of four pars to remain one-under after nine holes.
Elsewhere Darren Clarke, playing with Spain's Miguel Angel Jimenez and American Craig Stadler, reached the turn in level par.
The defending champion Vijay Singh made his way onto the course shortly after 5pm Irish time and is level par after six holes. The tournament favourite Tiger Woods began his challenge an hour later and he too is level after three holes.