At 43, Dom Meffe Jr. has lived the life of several entrepreneurs--he owned (with his father) 13 Chuck E. Cheese's before turning 30, then ran the Weight-Rite golf-shoe company, then started a pharmacy-claims-processing company, then started a specialty pharmaceutical company. He sold that last company, CuraScripts, for $333 million in 2004, then ran it as a division of its parent company until revenue approached $4 billion.

So what next? Meffe's personal life had been rattled by cancer. His sister had died from a brain tumor, his wife had had a tumor removed, and he had been treated for testicular cancer. When some private equity people he'd worked with approached him about running a company that would work on cancer-diagnosis tools, Meffe jumped. He joined Triad Isotopes as CEO in late 2006.

The company makes nuclear pharmaceuticals, radioactive materials that help with diagnoses and treatments. One highly simplified example: If a doctor can't determine where a patient's infection is coming from, he can send the patient's blood to one of Triad's pharmacies, where pharmacists will tag the white blood cells with a gamma-emitting isotope. The doctor reinjects the treated blood into the body and later takes a photograph with a gamma camera. Because white blood cells attack infections, the gamma camera will pick up where those treated white blood cells have headed: to the kidneys, the liver, wherever, and the source of the infection is revealed. Meffe estimates Triad products will treat 900,000 patients this year.

Meffe's strategy with Triad has been to acquire existing companies, which has led his little Orlando start-up to $120 million in revenue in its first full year. You might think all his experience would make this a breeze, but no. "I'm a lot more experienced now," he says. "Some of the other companies I ran, I wasn't aware of the things we were doing right or aware of the things we needed to do. Now I know, and if I don't get it done, it's frustrating. There's so much to do. So much more to do."