The demonstration took place on Wednesday, two days after the visiting US Secretary of State Condoleezza Rice called for free expression for the opposition.
In previous protests, security forces have outnumbered protesters, surrounding them to prevent them from moving and sometimes scaring passers-by and stopping people from joining.
But police remained in their trucks on Wednesday, out of sight, while more than 300 protesters walked for two hours down a main street of the crowded working-class district of Shoubra, chanting "Kifaya" - Arabic for
"Enough!" - to President Hosni Mubarak.
"Down with Mubarak," they shouted, and "Gamal tell your father, all Egyptian people hate you," referring to the president's son.
A group of fewer than 100 Mubarak supporters nearby shouted back: "Gamal tell your father 70 million Egyptians love you."
"Down with Mubarak. Gamal tell your father, all Egyptian people hate you"
Cairo protest chants
Some took their shoes off, a sign of contempt, and made obscene gestures, but there was no violence.
The reform protest organisers chose Shoubra in an attempt to draw into their cause people normally not involved in politics.
The district - far from official buildings where such rallies usually take place - is one of Cairo's most populated areas, with seven million residents, a mix of Muslims and Christians.
Thousands of people lined the streets and hung out of windows and balconies to watch the march, some smiling, clapping and chanting along with the protesters. Some passers-by joined the protest.
Others looked shocked - or afraid - at seeing a protest. Some shopowners quickly shut their doors, fearing violence with police.
"Yes! Enough! We've had it, we're dying," Yasser Mohammed, the driver of a minibus, shouted from his window in support of the protesters as he drove past.
Hosni Mubarak has ruled Egypt
unchallenged for 24 years
Mahmoud Allam, a 75-year-old Shoubra resident, marched with his two grandchildren, Shimaa, 9, and Mahmoud, 6.
"I'm training them to learn about freedom and democracy, to know their rights and never give them up," he said.
Protest organisers were surprised by the security forces' absence. "Condoleezza gave them (the government) a hard time," one protester, Osama el-Goharay, said by way of explanation.
"Mubarak is still in power because of the Americans, not because the people want him."
Rice visited Egypt on Monday, meeting Mubarak and opposition figures.
She gave an address at the American University in Cairo urging Middle East governments to allow reform. "The Egyptian government must fulfill the promise it has made to its people and to the entire world by giving its citizens the freedom to choose," she said.
Rice visited Egypt on Monday
She also said demonstrators should be able to protest without fear of violence - a reference to a 25 May pro-reform demonstration in which government supporters beat participants and molested women while police stood by.
In the line of pro-government demonstrators on Wednesday, Hani Mohammed, a 28-year-old unemployed Shoubra resident, said Mubarak is being "humiliated" by the criticisms at home and abroad.
"I felt I have to say something, even though I'm suffering economically. Mubarak is under a lot of pressure, we're trying to help him," he said.
Wednesday's anti-Mubarak protest was organised by the Popular Campaign for Change, a group of mainly leftist activists.
With presidential and parliament elections approaching this year, Egypt has seen an unusual series of protests calling for an end to the 77-year-old Mubarak's 24-year rule.
They have been led by the Kifaya movement - a group formed from secularists, communists and Islamists - and by the outlawed Muslim Brotherhood.