© ReutersProtesters demanded the immediate resignation of the coalition government
They say 120,000 people packed the capital Prague, protesting against austerity measures and corruption. Police put the numbers at 90,000.
Echoing 1989, people jangled their keys - a signal to the centre-right coalition cabinet to lock up and leave.
The government has recently been rocked by splits and defections.
It is no longer clear if the coalition of Prime Minister Petr Necas commands a majority in parliament, the BBC's Rob Cameron in Prague reports.
'Anorexic'
On Saturday, the protesters - including many pensioners and students - marched through Prague, gathering in Wenceslas Square - the heart of the capital.
Chanting and whistling, they carried banners which read "Stop thieves!" and "Away with the government!"
Rene Koncilova, one of the marchers, said she was struggling to survive on her monthly $350 (£217) disability pension.
"Vaclav Klaus (current president) told us in 1989 that we had to tighten our belts, and the country became anorexic," she told the BBC.
"Fortunately, doctors managed to cure it, but now they're asking us to tighten our belts again. I think we'll all be anorexic before long."
The government says there is no alternative to cuts in public spending and tax rises if the country is to avoid the fate of debt-ridden Greece.
People here in Czech republic are definitely getting pi**ed off by everything what happened during past 22 years. The country had no debt - now it has 50 billions Euro state debt. There were well working social system - completely free health care, dental care included, there was right for work - have you heard about that before? You had right to get work. Funny? No, that is how it was. There was one of the best agriculture system all across the country, which is nowadays in ruins, destroyed, not working. All the state, common property was mostly during the 1st decade made private. Unfortunately, all this was not covered by proper laws on demand and constant push of Mr. President Klaus, who is considered a Thief Nr. 1 in the Czech republic. Basically all the heavy industry was sold and in many cases closed right after. Just an exmple - in my town, there was the main production site of Heavy-lifting storage vehicles with international fame and success - Desta. Sold to speculants and destroyed. There was huge chocolate products factory Diana - chocolate of this mark was exported all across the europe. Sold to Nestle, closed right after - destroying of competition. And it is a town of 55 thousands people. The story like this goes all across the Czech republic, with different curcumstances and one same thing - the privatization - the sold out - was not to make it better managed, but to steal it to invest groups, who did right just the best to make immediate profit, without any reflection of wider consequences.
This way was made in the Czech republic a new elite mostly consisting of those, who knew how to make the best and biggest theft during the privatization and the net of cessions is absolutely unfindable. Even Czech corruption police is not able to find out who owns what, because by these thieves owning Czech republic now made the ownership spread into thousands of strangely named foreign-countries, mostly tax-paradises, registered companies.
22 years before, people was all happy to get democracy, unfortunately the worse people, in front with Vaclav Klaus and weak puppet-president Vaclav Havel, got into leadership of our country, which is these days most probably one of the most mafia-organized countries in the middle Europe.
We usually use to call our country a Stolen out country.