NEW YORK (AP) _ Some heirs to great family fortunes dabble in art collecting. Others become renowned philanthropists.

Ola Stillman Rockefeller is posing for underwear ads.

Rockefeller, 30, is the newest pitchman for Jockey International Inc. The company unveiled the magazine ad campaign at a news conference Tuesday with the aid of baseball great Jim Palmer, who is perhaps the best-known Jockey model.

Rockefeller, according to material provided by his public relations agency, has a ''recent penchant for art.'' He has collaborated on collages with Mark Kostabi, a New York artist who has mounted public relations stunts to promote his artworks.

Rockefeller said Jockey came to him with the idea of posing for the ads.

''I kind of hemmed and hawed,'' he said in an interview. ''I really wanted to do it but then I thought, 'Is my grandfather going to kill me or cut me off or something?' But I eventually decided to do it. I'm just sort of winging it.''

He said his grandfather, James Stillman Rockefeller, former chairman of First National City Bank of New York, opposed the plan until the younger Rockefeller said he would give the proceeds to Memorial-Sloan Kettering Hospital, a family charity.

''In some ways I am trying to create my own identity,'' Rockefeller said. ''Sometimes it's hard if you're the son of or descendant of - you're expected to play a certain role.''

Rockefeller said he hopes the exposure he gains through the ads - in which he is tastefully garbed in plaid undershorts and a T-shirt - will help further his art aspirations.

Rockefeller, whose great grandfather was a brother to John D. Rockefeller, the founder of Standard Oil Co., said he's been wearing Jockey underwear since he was 14.

One of Rockefeller's cousins, James Stillman Rockefeller Rose, said Rockefeller's plan to pose for the ad ''sort of came out suddenly.''

''The only reason the family let him get away with it is that he's donating the procedes to Sloan-Kettering,'' Rose said in a telephone interview.

Several years ago, Rockefeller announced he would launch a line of men's clothing featuring the family crest. The clothes never materialized, ''thank God,'' Rose said, adding that the family was dismayed by the intended use of the crest.

Rose, 30, described his cousin as the non-traditional member of an otherwise low-key family.

Rose, who helps manage a family-run investment company, said that despite the trust funds - the total of which dwindles with each generation - most members of his generation of the Rockefellers are employed.

''We've have a much stronger work ethic than a lot of our cousins on the other side of the family do, out of necessity and training,'' he said.