GCI Atlanta president Ken Willis assumes the mantle of chairman of the new entity.
Joel Babbit, 360 co-founder and CEO, becomes president and chief creative officer of the combined shop.
Mark Goldman, 360 president, will head the advertising arm, Grey Worldwide, as its president.
At GCI Atlanta, Bob Cohn becomes chairman, while Jim Overstreet becomes S-VP. Cohn and Overstreet joined 360 in 2000 after they retired from Cohn & Wolfe Atlanta.
The deal was preceded last November by an alliance in Atlanta between Grey World-wide and 360, when they teamed up to win the lucrative BellSouth ad account.
Earlier in the year, 360 partnered with Porter Novelli Convergence Group in an effort to win BellSouth's PR business, previously held by GCI Atlanta.