Lehman fired a 7-under-par 64 on the TPC at Scottsdale to tie Scott Verplank and Brad Elder for the 18-hole lead.
Tiger Woods is in a group one off the lead. Woods, Stewart Cink, Frank Nobilo, Chris Perry, Mark Calcavecchia and Steve Pate each opened in 6-under-par 65.
First-round play was suspended due to darkness. Nine players were left on the course. They will complete their rounds Friday morning.
Elder set the early pace, coming home in 6-under-par 30. Playing in his second full season on the PGA Tour, the former collegiate Player of the Year at the University of Texas birdied holes 13-17 to grab a share of the first-round lead.
'I had my putter going really well on the back,' said Elder, who was inadvertently introduced in the pressroom as Lee Elder, who in 1975 became the first black player to compete in the Masters.
Lehman's title defense began auspiciously with a bogey at the par-4 10th. But an eagle at the par-5 15th turned around his round. Lehman added a birdie at the 18th to make the turn in 2-under; and then proceeded to blister the front nine.
Lehman, who opened in 63 a year ago, birdied his first three holes on his inward half, and added two more on holes five and nine for a nine-hole score of 5-under-par 30.
'The first four holes I made terrible strokes and decided, hey, forget about your stroke and just putt it,' said Lehman, who took 26 putts in the first round. 'Just don't try to make the putt. Don't worry how you do it. From that point on, I putted well.'
Like Lehman, Verplank used an eagle at the 15th to jumpstart his round. Last year's Reno-Tahoe Open winner played his first seven holes in 5-under en route to a bogey-free round of 64.
Tiger also went around the Scottsdale track without a bogey. Making his first Phoenix start since a third-place finish in 1999, Woods carded six birdies in his round of 65.
'It could have been better but I had a couple of lip outs,' Woods said. 'I was playing well in practice, so it was just a question of bringing it into the tournament.'
Tiger nearly added his name to the top of the leaderboard but was distracted by an orange tossed by a spectator before he made his birdie attempt at the ninth hole, his last. Tiger backed away from the 20-foot putt, looked into the crowd, and then missed the putt.
Police detained the spectator who threw the orange. Tournament officials said they plan to press charges.
One of Tiger's birdies came courtesy of a two-putt at the par-4 17th. Woods was one of many to drive the 333-yard hole, though none matched the dramatics provided by Andrew Magee.
Just seconds after Pate converted an eagle putt from off the green, Magee felt compelled to hit his driver. The ball carried the full distance, ricocheted off the putter of Tom Byrum, who was playing in Pate's group, and rolled into the cup for a hole-in-one.
'I'm still in shock,' Magee said following his round of 5-under-par 66. 'I'm going to bask in the glow of this for a while.'
The unorthodox ace is believed to be the first hole-in-one on a par-four in PGA Tour history.
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