Jay Haas, Andy Bean, Morris Hatalsky and Wayne Levi were two shots off the pace at 5-under-par 67 at The Westin Savannah Harbor Resort and Spa.
'I knew I was playing good coming in here,' said Purtzer, a two-time winner on the Champions Tour. 'Even after the three-putt at No. 2, I told myself to be patient.'
At the par-4 ninth, Purtzer played his second shot to 15 feet and drained the putt to climb to 3 under. He hit his approach to 6 feet for a birdie at the par-4 10th and two-putted for a birdie at the par-5 11th to make it four in a row.
Purtzer kept on cruising at the par-5 13th and chipped for another birdie. He then landed his second shot inside 4 feet at the par-4 14th and rolled in the putt to move into the lead at 7 under. Purtzer then parred his four remaining holes to hold the 18-hole lead on the Champions Tour for the first time since last year's 3M Championship.
'I've gotten to a point where I feel good on this course,' said Purtzer, whose best finish at this event is a tie for sixth last year. 'Ideal conditions today. I got into a stretch where I had the right clubs and could go at some pins.'
Smyth jumped out of the gate with a pair of birdies over his first three holes and added a birdie at the eighth to make the turn at minus-3. Smyth then hit his second shot to 10 feet for a birdie at the 10th and jumped to 5 under with a birdie at the 14th.
The Irishman ran home a 12-foot par putt at the 17th and knocked an 8-iron within 15 feet at the following hole. Smyth sank the birdie putt at the last to finish within one of Purtzer.
'I'm delighted,' said Smyth, who captured this year's SBC Classic. 'Not going to think about winning yet. This is only one round and there's a long way to go.'
Larry Nelson, Craig Stadler, Gary Koch, Gil Morgan and Jim Dent share seventh place at 4-under-par 68. Ben Crenshaw, Mark Johnson, Leonard Thompson, Dana Quigley, J.C. Snead, Jim Thorpe, Charles Coody, D.A. Weibring and Tom Kite are one shot further back at 3-under-par 69.
Defending champion Hale Irwin struggled early with four bogeys over his first nine holes. Irwin countered on the inward half with an eagle at the par-5 11th and three birdies over his last seven holes to finish in a group at 1-under-par 71.