Keith/Mack, one of Miami’s oldest and most venerable law firms, has put itself up for sale, amid staggering departures by both partners and associates.

In recent months, Keith/Mack, whose partners include Miami Beach Mayor Neisen O. Kasdin, has lost nine lawyers, and managing partner Robert A. Cohen said the firm is currently being wooed by one or more national firms interested in establishing or buttressing an outpost in South Florida. The partners, he said, are seriously considering a merger.