Jason Day leads Aussie charge at Tiger Woods's National PGA event

Jason Day leads Aussie charge at Tiger Woods's National PGA event, Tiger Woods wanted his PGA event to play like a tough US Open-style test and the world number one got his wish in the opening round of the National at Congressional Country Club.

Thick rough and narrow fairways on the layout where Rory McIlroy won the 2011 US Open kept players scrambling, although American Roberto Castro solved it for a 5-under-par 66 to seize a two-stroke lead after 18 holes.

"The golf course is all you can handle," Castro said.

"It's long. The rough is brutal. There's not a lot of birdies out there. You're just plodding along. The golf course hasn't changed much in two years."

Jason Day is the leading Australian at one-under, with compatriot John Senden a shot further back after an even-par round of 71.

Adam Scott, the reigning Masters champion who was third in this event the past two years, opened on 73.

Woods, absent while recovering from a left elbow sprain, serves as host for the $US6.5 million ($A7.04 million) event, which is run by his charity foundation.

He used the US Open as a course set-up guide, easing up only on green speed and hole locations.

"I would like it to be one of the more difficult PGA Tour events, there's no doubt," Woods said.

"It's green. It's lush. It's thick. Temperature's up. It's going to present a hell of a test for the guys."