Czech government steps down
The no-confidence vote had the support of 101 lawmakers, just enough to topple the centre-right minority government.
Topolanek's government had fought off four previous no-confidence votes since taking power in January 2007.
The present cabinet was strongly criticised for signing the agreement with the U.S. to place radar bases on the country's territory.
Recent polls showed two-thirds of the population opposed this decision.
The no-confidence vote automatically expands the powers of the nation's president, Vaclav Klaus, who now becomes a key figure in upcoming talks between political parties seeking to form a new cabinet of ministers. Under the national Constitution, Klaus has the powers to appoint a new Prime Minister.