Thousands of Slovaks are protesting in the capital to demand that top politicians accused of corruption step down.
Friday's rally in Bratislava is the third this year over corruption allegations in Slovakia.
In December, a file known as "Gorilla" _ allegedly compiled by the country's SIS spy agency _ appeared on the Internet suggesting that the financial group Penta had bribed government and opposition politicians in 2005-06 to win lucrative privatization deals.
Police are investigating the allegations, but SIS has not confirmed the document's authenticity. Penta and the politicians named have denied wrongdoing.
Another rally is planned for Feb 19.