Canadians Sarah Reid and Mellisa Hollingsworth are first and second after two heats in the skeleton World Cup opener in Lake Placid, N.Y.
Reid had a combined time of one minute 51.72 seconds, just 0.02 ahead of her teammate at Mount Van Hoevenberg. Marion Thees of Germany was third.
Reigning world champion Katie Uhlaender of the United States rallied after a poor first run with the second-fastest time on the second and was sixth, 0.70 off the lead.
"The field is so strong, ridiculously strong," said Hollingsworth, a Eckville, Alta., native who finished second behind Uhlaender at worlds. "You look at the top 10 and any given day any one of those girls can be on top of this podium. I definitely don't take it for granted that we're going into tomorrow with a little bit of a lead."
The race is a three-heat event, and only the top 10 sleds qualify for the final heat.
For Calgary's Reid, the day was a big surprise.
"I had really good training days and things were kind of coming together," she said. "But my best result in the World Cup is sixth place, so to be sitting in first going into day two I'm pretty excited."
On the men's side, Martins Dukurs of Latvia has a slim lead over Alexander Tretiakov of Russia and brother Tomass Dukurs after two heats.
Martins Dukurs finished in 1:47.71, just 0.01 ahead of Tretiakov and 0.06 ahead of Tomass Dukurs at Mount Van Hoevenberg.
Reigning Olympic champion Jon Montgomery of Russell, Man., who did not race last season, was 12th, more than two seconds behind.
"I wish that it was a better day," said Montgomery, who spent a good deal of the previous day repairing his bent sled. "There's got to be building blocks, one step at a time — two back, one forward.
"Essentially, it was a whole new sled, and that's tough to have any measure of consistency, and the name of the game is consistency," he added. "I can't be too disappointed in reality, but the fact is I'm hard on myself. I always want to be in the mix and I'm not in the mix. I wish that I was further ahead, but I also have to be realistic about my expectations and know that nobody gives two hoots about today. It's one year and four months (at the Winter Olympics in Sochi) that's the deal. I've got to keep my eye on the prize."
The opening race of the World Cup season consists of three heats, and only the top 10 after the first two heats will race for the gold medal on Friday.
American Kimber Gabryszak missed the cut at 13th after the first two heats and a mistake-filled first run.
"Ironically, it's almost a relief," Gabryszak said. "The competition here is extremely intense. I'm just glad to be here. I had a really rough first run, but the second run was good, so I'm happy with that.
"There is a little rust remembering how to handle the pressure of a World Cup. I used to hate this place, but it's grown on me. I really thought I had a chance at the top 10, but that first run just killed me."
The U.S. women's team is attempting to qualify a third sled for worlds in St. Moritz, Switzerland, in late January. Currently, Great Britain, Germany, Canada and Russia have three.