Protests were held in Madrid, Barcelona and other cities
Thousands of workers have protested in Spain's major cities against government spending cuts and plans to raise the retirement age by two years to 67.
The rallies were the first mass labour protests in the six years of Prime Minister Jose Luis Rodriguez Zapatero's Socialist government.
He announced 50bn euro ($67.5bn; £43.8bn) spending cuts and a civil service hiring freeze in January.
Spain faces a large budget deficit, a sluggish economy and high unemployment.
The main demonstration was in Madrid, where union officials said 60,000 protested. Police put the crowd at a much smaller 9,000 people.
"Mr prime minister, don't play around with pensions, with the future of millions and millions of people in our country," said union leader Ignacio Fernandez Toxo in a speech at the rally in Madrid.
Mr Zapatero also wants to change Spain's rigid labour laws to make it easier and cheaper to hire workers.
Spain's rising debt has prompted scrutiny from bond markets worried about a Greek-style budget crisis.
But the head of the Organisation for Economic Co-operation and Development (OECD), Angel Gurria, said on Tuesday that Spain's public debt was manageable and not comparable to Greece's.