German Chancellor Angela Merkel's Christian Democrats have lost the key state of Baden-Wuerttemberg after six decades, preliminary results show.
The results gave the Greens 24.2% and their Social Democrat allies 23.1%, with Mrs Merkel's party on 39% and its Free Democrat (FDP) allies on 5.3%.
Nuclear power, following the accident in Japan, was a key issue.
The vote in the wealthy south-western state was seen as a referendum on Mrs Merkel's rule.
The region, around Stuttgart, has a population of some 11 million and has been ruled by the Christian Democrats since 1953.
http://www.bbc.co.uk/news/world-europe-12876083
Note: 27 March 2011 Last updated at 21:01 GMT