At 90, Bill Stern is 46 years into his running career–and set to compete in the 2009 Summer National Senior Games at Stanford University in August.

A native of Ohio, Stern graduated from MIT with a degree in chemical engineering, adding a master’s degree in chemical-­engineering practice in 1941. “MIT was superb,” he says. “I was like a kid in a candy shop.” Then his U.S. Army ROTC commission took him into the North Pacific–Alaska and the Aleutian Islands–during World War II. At the end of the war he returned to civilian life and journeyed to Texas, where he met his wife, Helen. “The minute I saw her, the angels started to sing, and they never stopped,” he says.

In 1961 the Sterns moved to Lexington, MA, where they raised their four children. The couple loved hiking in the White Mountains; Stern, now a life member of the Appalachian Mountain Club, had climbed all the 4,000-footers by 1978. They moved to a retirement community in Bedford, MA, in 2005, and Helen died in 2008.

Stern, who has always enjoyed measuring things, began working in instrumentation in 1950. His career focused on domestic and international marketing of sensing, measuring, and recording equipment. In 1970 he teamed up with two MIT professors to guide the successful growth of the startup Setra Systems, which designs and manufactures sensors and controls.

Stern retired in 1986, but he did not slow down. A member of the venerable Cambridge Sports Union running club, he completed a Boston Marathon in 1986 and has run many other U.S. races, including the torturous seven-mile run up Mt. Washington. He continues to exercise nearly every day–walking, jogging, running, or exercising in the pool–and belongs to the New England 65 Plus Runners Club. This summer at the games, he’ll compete in the 100-meter, 200-meter, and 1,500-meter distances, marking his fourth appearance at the Senior Games.

Next June, Stern plans to attend his 70th MIT reunion, with his eyes as much on the future as on the past. In fact, ask him about his favorite race and he’ll tell you that he subscribes to that old running adage: “Your favorite race is always your next one.”