Williams chief designer Jorg Zander has left the team with immediate effect for personal reasons.
Zander joined WilliamsF1 in September 2005 after two years as BAR's chief engineer of mechanics and transmission.
Zander's departure is said to be unrelated at all to his work performance, and Williams said they would not be seeking an immediate replacement for the German.
"Unfortunately Jorg had to leave for personal reasons, and we wish him and his family well in the future," a team spokeswoman told autosport.com.
"We firmly believe that the technical structure we have in place in our design office is strong enough to withstand Jorg's departure, and it will not affect the development of the FW28 this year, or the design of the FW29 for 2007."