What might have been the advertising trial of the decade is off.

Peter Arnell and his former employer, Omnicom Group, have settled their lawsuit over the ad and design guru's library. The New York State Supreme Court's electronic database today identified the case as disposed, and a court employee said the case had been settled. Terms were not available.

In the lawsuit, Mr. Arnell insisted that Omnicom return an expansive library, bought partially with company money, or pay him about $1 million. Mr. Arnell, whose Arnell Group was purchased by Omnicom in 2001, was terminated last February, a few days before the suite was filed. In a surprise move, Omnicom named Sara Arnell, Peter's wife and longtime Arnell Group employee, CEO of the agency.

Reached by phone in Europe, Mr. Arnell declined to comment on the settlement. Omnicom spokeswoman Elizabeth Watters didn't return emails or telephone calls. Ms. Arnell did not immediately respond to an email seeking comment.

According to the complaint, the library contained "rare, unique, one-of -a-kind, signed artist's volumes, first editions, photographs, catalogues, photography volumes, volumes of important works of architecture" and Mr. Arnell's personal portfolios. They are, the lawsuit said, "the tools with which [Mr. Arnell] conducts his intellectual business life."

Some of the books were in the collection before Omnicom acquired Arnell; others were bought as a "business expense" partly covered by Omnicom, the suit said.

Various motions had been filed over the past year, and it seemed the case was inching toward trial -- a prospect that had Madison Avenue spinning. After all, Mr. Arnell's story is the stuff of legends, chock-full of big stars, big ideas and big controversy that has provided no shortage of entertainment.

Brands like Home Depot, PepsiCo and Chrysler flocked to Mr. Arnell's shop in past years, seduced by his design sensibility. Along the way, there were more than a few missteps, including the leak of an esoteric memo about Pepsi 's logo redesign--a project he later described to a reporter as "bullshit" -- and a Tropicana package makeover that consumers hated and the brand quickly undid.

By the time he left Arnell Group, it had just a handful of clients, and the onetime secret weapon of Omnicom had clearly seen his relationship with his bosses sour.

There's been much industry speculation about the Arnells' relationship but no official indication they've separated. Last year, Ms. Arnell put up for sale the Katonah, N.Y., mansion they bought from music exec Tommy Mottola, asking $22 million. The Wall Street Journal article that broke the news made no mention of Mr. Arnell, and Ms. Arnell said she would soon be an empty-nester.

Mr. Arnell has been uncharacteristically quiet about his next move. Today he was mum on his future prospects. "There's nothing to talk about yet."