Spokesmen for the organisers, Kifaya (Enough), said the police arrested 125 protesters but all except two had been released by nightfall.
Witnesses in some cities, including Suez in the east and Benha in the Nile Delta, reported that police beat protesters with batons to disperse them.
The organisers said they were pleased that the protests to press for reforms had spread from Cairo to the provinces.
"We are expanding to cover all of Egypt," said Amin Iskandar, a leader of the group, Egyptian Movement for Change.
The spokesmen said they chose to protest in front of courthouses on Wednesday as they wanted to demonstrate support for the judges who have called for political reform and a free hand in monitoring the presidential and parliamentary elections in September and November.
"We are expanding to cover all of Egypt"
Egyptian Movement for Change
In Cairo, hundreds of riot police barred 300 protesters from the Supreme Court, so they assembled on the steps of the nearby journalists syndicate.
"Down with Mubarak, down with Sulaiman," the demonstrators chanted, referring to President Hosni Mubarak and his chief of intelligence, Omar Sulaiman.
Many protesters held aloft placards saying "Enough".
Several young people moved through the crowd soliciting members for an offshoot group, to be called Youth for Change.
"We're trying to make a group for younger people in order to address issues of unemployment and such ... under the slogans of Kifaya," said Sarah Naguib, a youth activist.
In the southern city of Aswan, 50 protesters managed to pass a police line to the local court, but they had to leave their banners behind.
Many Egyptians want President
Mubarak to step down
About 1200 people rallied in the southern city of Luxor.
"This is the first time [in Aswan]," said a local Kifaya organiser, Muhammad Abbas, an electrician. "This is success. Aswan broke the silence."
Hundreds also gathered in the southern cities of Minya and Qena and at venues in northern Egypt including Alexandria, Suez and Benha.
Protests calling for an end to Mubarak's rule, the repeal of emergency laws that give security forces broad powers, and pro-democratic reforms, have been growing in Egypt.