Thomas Mac Mahon, chief executive officer at LabCorp for a decade who then became the firm;s chairman, is retiring from the board of directors.

LabCorp (NYSE: LH) announced Mac Mahon’s decision Thursday after the markets closed.

Mac Mahon served as CEO from 1997-2006. He then served as non-executive chairman of the board from 2007-2009. He will not seek re-election to the board when his current term expires next May. He has served on the board since 1995.

“Tom has contributed immeasurably to LabCorp during his 30-year association with LabCorp and the diagnostic industry,” said David  King, the firm’s current CEO and chairman. “On behalf of the Board and the 31,000 employees of LabCorp, I would like to express our deep gratitude for his years of dedicated service.”

In another move, LabCorp said Peter Neupert would join the board as of Jan. 1, 2013. Neuptert is operating partner of Health Evolution Partners, a private equity firm.