Their mission is simple - to raise awareness of canine cancer. The trip began March 16, 2008, in Austin, Texas, and will end in May 2010 in Boston.

But Robinson's journey really began in 2004 when another of his "boys," Malcolm, was diagnosed with osterosarcoma, a bone cancer. The playful 6-year-old Great Pyrenees lost a leg to the disease and endured rounds of chemotherapy before he was "given rest" in 2006, Robinson said.

"I'd never experienced that closeness, that spiritual bond with an animal before," he said. "We did everything together. I'd golf, and he was my caddy. He'd ride shotgun in the golf cart."

Robinson was devastated by the loss but decided to turn Malcolm's death into something positive. The founder of a high-tech and life science consulting firm and his dogs began preparing for their travels.

"We had to train for this, and it took many, many months," he said. "It's work, but (Great Pyrenees) are a working breed. That's the ideal life for them."

Robinson next sold his truck, put his belongings in storage and strapped a pack on his back, ready to roam the United States. He knows this trip won't be a short one.

"It's only the first phase of a life-long commitment," he said. "I promised Malcolm I'd devote my life to this."

Malcolm also is part of the journey, with Robinson wearing a small ring on a chain around his neck which contains some of Malcolm's ashes.

Robinson said the statistical data available regarding canine cancer is limited. In his experience talking to veterinary oncologists throughout the country, he's noticed two trends - cancer in dogs is more common, and the average age of diagnosis is getting younger.

"If this continues, where are we going to be in a couple of decades?" he said. "It's no longer just about prolonging life; it's about saving lives."

The team travels 8 to 10 miles per day, taking frequent breaks to conserve energy and prevent heat exhaustion. In 16 months, they've experienced everything Mother Nature can throw at them, from tornadoes and hurricanes to blizzards and ice storms.

Even the worst of weather can't deter them from their mission.

"We're all about awareness - education, outreach and awareness," Robinson said. "Unless you've had a dog with cancer, you've probably never thought about it."

Throughout the trip, Robinson has encountered numerous people who've lost canine companions to a variety of diseases. He, Murphy and Hudson like to spend time interacting with locals in each town, visiting elementary schools for show-and-tell and volunteering at local humane societies.

The trio arrived in Pittsburgh June 30, just in time to catch "Pup Night" with the Pittsburgh Pirates at PNC Park.

They also took in the city's Fourth of July fireworks from the Western Pennsylvania Humane Society.

Robinson relies on the kindness of locals for lodging. His traveling pack includes a tent that he has pitched on the side of the road before, but he prefers the security of a yard whenever possible.

Friday night's camp was at Marei Burnfield's home in the Blythedale section of Elizabeth Township.

Burnfield heard about Robinson's travels and wanted to help. So she opened her home to the trio.

"She is typical of the kind of people we meet," Robinson said. "People have been phenomenal, gracious, giving, generous."

"Luke and the boys," as their followers on their Web site www.2dogs2000miles.org call them, plan to follow the Great Allegheny Passage to Washington, D.C., and cross the Potomac River in September "with as many people who will join me."

Robinson already has plans to continue his work in the U.S. and is contemplating a "2 dogs, 2,000 kilometers" campaign in Europe.

He knows each step might bring him closer to the cure for canine cancer.

"Dogs need someone to speak for them, to fight for them," he said. "That's what I feel my mission is."

Robinson said there are moments when he sits back and realizes he's living the opportunity of a lifetime.

"I love the adventure ... the hearts that we can touch, and the people we can reach out to," he said. "It all comes down to getting the word out there.

"The most unexpected things happen in the most unexpected places. This country is an awful beautiful place, if you have the courage to see it.