Sonnenschein Nath & Rosenthal is adding new partners at its fastest clip ever and has added three new offices this year, yet attorney head count is expanding only slowly toward a 2009 target of more than 1,000 lawyers as some lawyers leave.

Despite signing up 20 lateral partners so far this year, the total number of attorneys at the firm has grown by five — to 650 — because some attorneys are exiting as the firm sharpens its strategic focus, the firm’s chairman, Elliott Portnoy, said in a recent interview.