HYANNISPORT, Mass. — Senator Kennedy took the helm of his sailboat “Mya” today and rode a stiff southern wind from Nantucket back to Hyannis in a regatta just a week after undergoing a brain biopsy that diagnosed him with cancer.

The Massachusetts Democrat made partially good on a pledge from the prior week by competing in the second half of the “Figawi” boat race between the island and Cape Cod. He missed Saturday’s outbound leg but got up early on Memorial Day and took a ferry across Nantucket Sound to compete in the return leg.

Also aboard for the more than two-hour journey were his wife, Vicki, Senator Dodd, a Democrat of Connecticut, and relatives including sons, Patrick and Edward Jr., and a stepdaughter, Caroline Raclin.

“It couldn’t be a more wonderful day,” Mr. Kennedy told several dozen well-wishers and a handful of reporters who greeted him dockside just down the street from his family’s vacation compound.

The senator said he relished the company of “great friends and family” while Mr. Dodd, Mr. Kennedy’s closest friend in the Senate, and Vicki Kennedy nodded in agreement.

Mr. Kennedy and his wife declined to discuss his upcoming treatment. Doctors are considering using chemotherapy, radiation, or a combination to treat the tumor that triggered a seizure on May 17. Treatment could start as early as this week.

Mr. Kennedy planned to compete in the Figawi even after doctors determined last week that he suffered from a malignant brain tumor.

Mr. Kennedy has won the Figawi contest twice.

“He was at the helm the whole way, doing what he always does, guiding the boat to the head of the fleet,” a family friend and an associate who regularly races with the senator and was on the boat as a crew member, David Nunes of Colorado, said.

After the race was over, the group sat at anchor off Hyannisport for an hour before coming ashore. “We always like to rehash the race,” Mr. Nunes said.

Mr. Kennedy has had a limited public schedule since getting out of Massachusetts General Hospital last Wednesday.

Besides skipping the first part of the regatta Saturday, Mr. Kennedy also missed a commencement address he was slated to deliver yesterday at Wesleyan University. Instead, he asked the Democratic presidential contender, Senator Obama, to address the graduates — including a stepdaughter, Caroline — at the Middletown, Conn., campus