The first day of the three-week tour is known as the prologue and, just as the name suggests, it provided a taste of what is expected to come.
Armstrong completed the 4.04-mile distance in nine minutes, eight seconds as the 89th edition of the world's most famous cycling got underway. He also won the prologue in 1999 en route to his first of three straight championships.
A victory in the prologue means little in the overall race since the top finishers Saturday were separated by only a few seconds. Once the mountain stages arrive during the second week of the tour, Armstrong will likely put several minutes between himself and his challengers.
But Armstrong wanted to demonstrate to his rivals Saturday that he is ready for this year's ordeal and he did so, powering his way up the final slopes to grab the yellow jersey that goes to the race leader. Armstrong and his United States Postal Service team may not try to protect the lead during the upcoming flat stages, likely saving their energy for the team time trial and the mountain climbs to come.
"It's good for us and it's nice to have the yellow jersey any time," Armstrong said. "I love the race and the motivation that comes with it. Being conservative is a good idea to start with. We'll try to be smart."
Armstrong has won his three straight titles thanks chiefly to his climbing prowess through the Alps and Pyrenees. Last year's victory in the 20-stage race elevated the Texan to the upper echelon of cycling royalty. He joined Frenchmen Louison Bobet (1953-55) and Jacques Anquetil (1961-64), Belgian Eddie Merckx (1969-72) and Spaniard Miguel Indurain (1991-95) as the only riders to win at least three consecutive tours.
This year, Armstrong is looking to join Anquetil, Merckx, Indurain and France's Bernard Hinault (1978, 1979, 1981, 1982, 1985) as the only cyclists to win the race more than three times.
Armstrong is recognized among the world's most courageous athletes after battling back from life-threatening testicular cancer to capture the 1999 event. In 2000, he cemented his place among cycling's all-time greats, becoming the first American since three-time champion Greg LeMond (1986, 1989 and 1990) to claim back-to-back titles.
Following Armstrong and Jalabert in the prologue were Raimondas Rumsas of Lithuania, Santiago Botero of Colombia and David Millar of Britain.
American Tyler Hamilton, touted by Armstrong as being one of his major threats this year, finished 16 seconds behind Armstrong Saturday.
Germany's Jan Ullrich was expected to be a fierce challenger, but he failed an out-of-competition drug test and will not be racing this year. He tested positive for a controlled substance during his stay at a clinic, where he was recovering from a knee injury.
The 28-year-old German, who was convicted of drunk driving last month, already had said his knee injury would keep him out of this year's tour.