Mr. DiCaprio has three Oscar nominations, for "What's Eating Gilbert Grape," which he made when he was 19, "The Aviator" and "Blood Diamond."

He lit up when talking about movies and people that have influenced him, particularly Billy Wilder's "Sunset Boulevard." But personal questions are not appreciated. Just why is it that he dates all those supermodels?

"I've never really talked about that kind of stuff, and, very respectfully, I'm going to keep it that way," he said.

Leonardo DiCaprio's transformation into J. Edgar Hoover, the longtime director of the F.B.I., required hours in the makeup chair. [Photo/Agencies]

He'd rather stick to "J. Edgar," particularly that prosthetic makeup. He estimates that he spent about two weeks of the 39-day shoot as "old Hoover," which required sitting up to five hours a day in the makeup chair. "To stay in character and to fight the urge not to rip it off at times and to not feel trapped inside it is extremely hard," he said. "It's like you've been slathered in honey and wrapped in a giant duvet."

He did months of research to be able to inhabit Hoover fully. "The research of these roles is half the fun and half the challenge " maybe more," he said.

Dustin Lance Black, who wrote the "J. Edgar" screenplay, said Mr. DiCaprio dug up films of a young Hoover giving speeches. "Hoover liked to weave a lot of allusions of slimy, slippery animals into his speeches at that time," he said. "Leo loved it. He said, 'Come on, we've got to use this stuff.'"

(Mr. Black also remembers Mr. DiCaprio's fondness for German chocolate cupcakes. "Some of those pounds on later Hoover were not prosthetic," he said. "I'll say it. Leo got a little fat.")

It is unclear whether "J. Edgar" will be a hit, but Mr. DiCaprio has an insurance policy in that ever pesky "Titanic," first released in 1997, which will be rereleased in April in 3-D. He said he had come to terms with being associated with the dopey Jack Dawson.

"I've been to the Amazon," he said, "and people with no clothes on, and I'm not exaggerating, know about that film. I've accepted it."

The New York Times