Edward I. O’Brien, president of the Securities...

Edward I. O’Brien, president of the Securities Industry Assn. for 18 years, announced that he plans to retire later this year as head of Wall Street’s main trade group.

O’Brien, 63, is the second president in the SIA’s history. He joined the trade group in 1974, two years after its founding.

The SIA, which represents more than 600 brokerage and investment banking firms in the United States and Canada, said a search committee will be formed to seek a successor.