Venzago's initial four-year contract expires at the end of the 2005-06 season.
According to a statement from the symphony, the new contract is "evergreen": it will automatically be renewed annually, subject to mutual agreement.
"I absolutely love this orchestra," Venzago said in a statement. "It is amazing that more people don't know about it nationally or internationally. We must continue our work to make it visible to a larger audience. This is a challenge that interests me because I want to help make our extraordinary musical heritage a part of many more lives."
The Swiss-born conductor is also principal conductor of the Gothenburg Symphony. He has also served as artistic director of the Baltimore Symphony's Summer MusicFest, principal guest conductor of the Malm‹ Symphony, and music director of the Basel Symphony, Basque Euskadi National Orchestra, Graz Opera, Deutsche Kammerphilharmonie, and Heidelberg Opera.