Irish Taoiseach Enda Kenny has laid a wreath at the memorial to those killed or injured in the Boston Marathon bombing.
Last month's tragedy, caused by bombs planted at the finish line of the city's marathon where spectators had gathered to cheer friends and family, killed three people and injured more than 260.
One of the suspected bombers, Tamerlan Tsarnaev, died in a shoot-out with police. The city was locked down as police searched for his brother and suspected accomplice Dzhokhar Tsarnaev, who was found hiding in a boat hours later.
He was taken to hospital, where he was later charged with use of a weapon of mass destruction and malicious destruction of property resulting in death.
The Taoiseach visited the memorial at Copley Square during his US visit.
On Monday morning the Taoiseach will be a guest at a business breakfast event where he will promote Ireland as an excellent location for trade, business and investment.
Later that day he will receive an honorary doctorate at Boston College.
He has also been invited to give the commencement address to over 3,000 students of the graduating class of 2013.
The event, which marks the 150th anniversary of Boston College, will take place in the college football stadium, with an attendance of over 20,000.