BOSTON (AP) _ Bank of Boston Corp., the nation's 15th largest bank holding company, said Monday it agreed to buy BankVermont Corp. in a stock swap valued at around $60 million.

The acquisition is the first under Vermont's new interstate banking law. Under the deal, BankVermont shareholders will receive one common share of Bank of Boston for each common share of BankVermont.

BankVermont, based in Burlington, Vt., has assets of $667 million. Its principal subsidiaries are Bank of Vermont, the state's second-largest bank with 16 offices, and Oxford Bank and Trust, which has five offices in Maine.

Bank of Boston, with $30.46 billion in assets, owns banks in Maine, Rhode Island, Connecticut and Massachusetts.

Ira Stepanian, Bank of Boston president and chief executive officer, said, ''We have been looking at the Vermont market for some time and we believe the state ... has excellent growth potential.''