A Wall Street firm has joined the roster for a building now under construction at 360 Madison Ave.

The research and investment banking firm, Gerard Klauer Mattison, signed a 15-year deal for 83,900 square feet, The Post has learned.

The 25-story, 360,000-square-foot building is being completed on the northwest corner of 45th Street, and is one block south of Bear Stearns’ new headquarters.

Rents in the neighborhood for class-A space range from $60 to $90. No numbers were released for this deal.

“As a growing firm, it was important to find the right building to accommodate our needs as an investment bank and brokerage firm,” said Manny Gerard, the company chairman. “We really like the immediate area for doing business, plus the convenience of being near Grand Central.”

The company recently expanded into a third floor at 529 Fifth Ave., where they now have close to 45,000 square feet.

Their new space will be located on the third, fourth, fifth and 10th floors.

Cushman & Wakefield brokers Paul Glickman, Matthew R. Astrachan and Shawna O. Menifee, along with the company’s Strategic Agency Services Group, represented the building owner, the Kipp/Stawski Group. The investment bank was repped by John Maher of CB Commercial.

Tenants will take possession starting in February 2002, said Stacey Fabrikant, the owner’s representative.

“Times Square got all the attention, but it’s Madison that is being transformed,” said Fabrikant.