Mr ElBaradei called for "guarantees of fairness" for next year's election
Egyptian security officials have warned against any large gatherings to welcome home the former head of the UN nuclear watchdog Mohamed ElBaradei.
The Nobel laureate is considering running for the presidency in next year's election.
Egyptian media have been saying a hero's welcome is being planned for Mr ElBaradei when he returns on Friday afternoon after many years abroad.
Large public gatherings are illegal in Egypt and can be broken up by police.
Security officials have told news agencies any "illegal gatherings" at Cairo's airport to greet Mr ElBaradei as he returns would be met with a heavy security presence. He is expected at around 1300 GMT.
Mr ElBaradei, 67, has built a strong reputation as head of the International Atomic Energy Agency (IAEA), winning the Nobel Peace Prize in 2005.
He stepped down in November and is now seen as the most credible potential opposition challenger for the presidency.
He has said he might stand if there were reforms to guarantee a fair election.
President Hosni Mubarak, 81, has ruled Egypt for nearly 30 years and there is much speculation he is grooming his son Gamal to take over when he steps down.
Opposition and civil society groups have long complained the authorities have used emergency laws and the security forces to curb political freedoms.
The largest opposition party, the religious Muslim Brotherhood, is banned and its candidates have to stand as independents.
A campaign on the social networking website Facebook has become a focal point for those calling for Mr ElBaradei to run for the presidency.
The Facebook campaign is advising supporters to travel to the airport in groups of three - the maximum number allowed to associate together in public.