Stenson made the most of excellent conditions at Thousand Oaks
(US unless stated):
-6 H Stenson (Swe)
-4 T Woods, G Ogilvy (Aus)
-3 F Couples, P Casey (Eng), C Montgomerie
(Sco), John Daly
-2 C DiMarco, J M Olazabal (Spa)
-1 David Howell (Eng)
Sweden's Henrik Stenson birdied three of the last four holes to move two shots clear in the first round of the Target World Challenge on Thursday.
US Open champion Geoff Ogilvy also got to six under but double-bogeyed the last for a 68 to share second place with tournament host Tiger Woods.
John Daly was a further stroke back in fourth with Fred Couples and Britain's Colin Montgomerie and Paul Casey.
Woods said: "I hit it decent but my speed on the greens wasn't very good."
England's David Howell finished one under, five shots off the lead, with compatriot Luke Donald struggling on four over.
Woods rattled up five birdies and a bogey on his way to a 68 but was unhappy with his putting.
He said: "I had two three-putts out there and I had to make a few others to avoid further three-putts.
"I'll work on my putting this afternoon and hopefully it will be better tomorrow.
"I've got to get my speed under control for the rest of the week."