"That's enough" and "Down with Husni Mubarak" shouted protesters who gathered in front of Cairo University on Monday, while around 50 trucks packed with police were deployed nearby.
A triple cordon of police, wielding batons and shields, surrounded the protestors, blocking other city residents from joining them.
"A quarter of a century in power is enough" and "Mubarak, admit you're a despot", the protesters chanted, brandishing banners ith the slogan "No to hereditary power" - a reference to steps being taken by the government to groom Gamal as a possible successor.
Organised by the Egyptian Movement for Change, the demonstrators also included Marxists, Nasirites, liberals and Islamic dissidents from the Muslim Brotherhood.
Leaflets handed out at the rally called for a constitutional amendment which would limit the president to two, four-year terms in power, instead of an indeterminate number of six-year terms.
They condemned the decision of some opposition parties to postpone demands for constitutional reform until after Mubarak's re-election vote.
The protesters are seeking a
"Such a delay would signify indefinite postponement of reforms and open the door to immense tension and foreign interference in Egyptian affairs," they said, alluding to calls by Washington for democratic reforms.
Under the Egyptian political system, parliament will elect a single candidate for the presidency in May, whose name will then be put to a referendum in September or October.