Eric Martin, 50; co-founded City Sports

In the middle of a working day, Eric Martin did what few company presidents would contemplate: He emptied the main office for a competitive game of roller-hockey. Other times, he would break for ping-pong in the company's workout room - and usually win.

"Eric was a funny character and a very charismatic and powerful personality," said Michael Kennedy, the chief executive of City Sports, which he founded with Mr. Martin in 1983. "When he wanted to play, we were playing in a short period of time."

A visionary retailer, Mr. Martin taught himself the art of attracting customers to City Sports stores, beginning with the first on Massachusetts Avenue down the street from the Berklee College of Music. An athlete with expansive tastes in sports, he brought his love of competition to building the store into a chain that now spans five states.

Mr. Martin, who met his business partner on a tennis court when they became doubles partners as 15-year-olds at Deerfield Academy, died of cancer Monday. He was 50 and had lived on Plum Island in Newburyport.

Perhaps the best-known articles of clothing his stores sell are the ubiquitous T-shirts in various colors that bear the City Sports logo, originally designed by Mr. Martin's sister Alison Martin Trumbull, who died in 2001. His family has asked that everyone who attends his memorial service later this month wear a City Sports T-shirt.

"Everyone has one," said his wife, Katie, "so we figured you might as well wear them."

Although the shirts come in gray and white, Mr. Martin preferred the more colorful incarnations - a taste he inherited from his late mother, Pat, who also instilled in him a love of dancing.

"She was a Californian and was like, 'We don't wear black,' " said his sister Kristi of Lincoln. "The house was full of colors."

His wife said: "I met him 30 years ago and I don't think I've worn black, brown, or gray since. I mean that literally."

The eldest of three children, Mr. Martin grew up in Groton Long Point, Conn., and began racing on skis before he was out of elementary school. He also was adept at soccer and tennis, which he played at Deerfield Academy and at Principia College in Elsah, Ill.

"The first time we met, we went at it on the tennis court hard and we were buddies from the first day," Kennedy said. "By fate, we ended up a doubles team."

They parted during college, when Mr. Martin and his future wife became friends. Joining a few other Principia students, they took off a winter semester to spend a couple of months in Breckenridge, Colo., and ski. And dance.

"He's a fabulous dancer - he's a swing dancer," his wife said. "We actually won a dance contest out there - my claim to fame."

Mr. Martin skied on the professional circuit for a few years after college. He then moved to Boston, where he worked as a stockbroker. Good fortune, he believed, was something to share.

"He didn't take his money and stuff it under his pillow and wait until 80 to live," his sister said. "When he got one of his first successful jobs as a stockbroker, he took his money and got us wonderful gifts. I still remember my purple angora sweater."

Mr. Martin and Kennedy were reunited when they both moved into homes in the Back Bay. The pair launched City Sports after realizing urban athletes had to travel elsewhere in the city to buy sporting goods. The first store was opened in 1983, the same year Mr. Martin married.

"We came to the conclusion that this was something we could do," Kennedy said, adding that the company's beginnings were hobbled initially by their lack of business backgrounds.

"We didn't know anything about it," he said. "We were off on just about everything you could be off on except for the main premise, which was that the area was desperate for a sporting goods store."

Mr. Martin brought to the venture energy and foresight, and he quickly developed a sense of what makes stores work. His father owned the Reid & Hughes chain of retail stores, where Mr. Martin had limited experience.

"He had good fashion sense," Stearns Martin of Groton Long Point said of his son. "He knew what he wanted to put in his stores. He knew the lines to put into the stores. But he didn't have any formal training in retailing, per se. He worked for me for two weeks after college.

"Most successful people go through a training program, but he didn't. He just did it."

"He had a natural eye as a merchant," Kennedy said. "He could swoop into a store and dust would be flying. When he left, the store would be much, much improved."

And Mr. Martin was savvy enough to know that T-shirts with City Sports logos would do more than simply contribute to sales revenue. Within a few years of launching the business, the stores were selling thousands of shirts each month. Customers sent in City Sports shirt sightings from across the country and around the world - all free advertising.

"You can't even put a dollar sign on that," Mr. Martin told the Globe in 1991.

An athlete always, Mr. Martin and his wife competed in a triathlon last year. At 48, he attended a ski racing camp at Mount Hood in Oregon and promptly got other participants to go out swing dancing.

"He was always looking for something new and fun to do - I know that's what my kids will miss the most," his wife said. "He was not a routine kind of guy."

In addition to his wife, father, and sister, Mr. Martin leaves two daughters, Gabby and Hannah; and a son, Cody.

A memorial service will be held at 3 p.m. on Sept. 22 in Cashman Park in Newburyport.