A crowd of between 20,000 and 50,000 people filled the square outside the Hungarian parliament building before the rally broke up around midnight. The PM admitted in a leaked private speech that his government had lied in order to win re-election this year.
The protesters have adopted white as their symbolic colour.
Rally organisers appealed to participants to add a white ribbon or wear a white item of clothing to symbolise, in their words, the need for truth and non-violence in the face of the PM's lies.
Mr Gyurcsany's socialist party has hit back, accusing the opposition conservative party, Fidesz, of responsibility for the protests and for the violence earlier in the week.
The socialists say their government has the support of the international financial community in its efforts to push through tax increases and cut benefits.
But, after a sixth night of demonstrations, the protests appear to be gathering steam again ahead of next weekend's local elections, the BBC's Nick Thorpe reports.
Nationalist flags
Demonstrations have also spread to several provincial towns.
Riot police question young protesters in Budapest The rally appears to have ended without serious incident
The mayor of the city has warned about the danger of violence, and large numbers of riot police have been on standby.
Rally organisers distributed flowers in what they said was a symbol of their peaceful intentions.
"Our protest will not cease until the cabinet resigns," said Tamas Molnar, one of the rally organisers.
"We want to bring down the current post-communist government."
Many of the demonstrators carried the pre-1945 Hungarian flag, a strong nationalist symbol.
On the first day of the protests, demonstrators stormed the state television building, set alight cars and vandalised the city's main Soviet war monument.
