At 67, Harrison Ford retains that roguish, lopsided grin that seems poised somewhere between a sneer and a smirk. His gray hair is thinning slightly and his face is more lined with years. But the man who became an icon as Indiana Jones and Han Solo says he's nowhere near retirement. He continues to make movies, he explains, because he simply wants to feel useful.

"I don't feel useful on the golf course or in Florida or in Arizona sitting on the back patio sipping iced tea," he says. "I feel useful on a movie set."

Ford is making himself useful these days, traveling the country to promote his latest film, "Extraordinary Measures," which opens today. The movie is based on the true story of New Jersey entrepreneur John Crowley — played by Brendan Fraser — who raised millions in capital and started a biotech company to develop a life-saving drug for his two young children, both of whom suffer from a rare genetic disease.

Ford plays an unconventional scientist whose discoveries are thought to be the key to finding a cure.

Coming to Chicago for a red-carpet premiere last week was a bit of a homecoming for Ford, who lived in an uptown apartment there until he was about 11 and who later moved with his family to the Chicago suburb of Park Ridge. At the restaurant inside the Four Seasons Hotel on Tuesday morning, Ford looks trim and handsome, as he sips a cup of green tea and talks briefly of hometown memories.

Ford doesn't spend too much time thinking about the old days. He notes he's "not a nostalgic guy." True to his word, Ford quickly gets down to business, ready to turn the conversation toward his most recent role, which is a "different character," he admits, than the ones he usually plays. In this film, he doesn't don a fedora or crack any whips; he doesn't accelerate into hyperspace or toss a terrorist off Air Force One.

What attracted him to this latest project?

"It's a fascinating modern story," he says.

The real-life events that became the basis of the film first caught his attention six years ago, he explains, when a literary agent pointed out a series of stories in the Wall Street Journal by Geeta Anand.

The articles followed the quest of Crowley, a one-time financial consultant, who — after being told that his two children had the fatal Pompe disease — quit his job, borrowed against his house, pursued scientists and eventually launched a company, all in an effort to develop a miracle treatment.

Ford says the newspaper stories "grabbed me emotionally." That initial reaction got to what Ford says he thinks is the very purpose of film making. "I've always felt that the whole object of movies is to provide emotional exercise," he says.

He became a champion for the project, signing on as executive producer, meeting with the Crowleys, helping select the screenwriter, carving out a part for himself and helping shape the script. It was a challenging project, he says, noting that he didn't want the film to become too "sentimental" or "weepy."

Facts were tweaked, the timeline was condensed and multiple scientists were rolled into one character, played by Ford.

Press materials say the film is "inspired by" real events. Despite changes, Ford feels that "we were truthful to the necessary elements."

As for Ford's future, there is word that a script for another Indiana Jones movie is in the works. But Ford makes it clear that he'll also make time for smaller projects.

"From the very beginning of my career, I've used the occasions where movies have been successful to do something different," he says. He mentions "The Mosquito Coast" (1986), a dark variation on "Swiss Family Robinson," and "The Frisco Kid" (1979), a quirky comedy/western.

In the end, he says, he's happiest when he's busy and working.

By doing a blockbuster one year, and a more limited release the next, he hopes to keep things interesting and, he says with a smile, "extend my useful life."