The arrests came after the group posted a notice on the Internet about the gathering, an official said.
There were conflicting accounts of the number of dissidents who arrived in Cairo. An airport official said only four had arrived so far, and they left the airport inconspicuously.
George Ishak, a spokesman for ElBaradei's group the National Association for Change, said 17 had arrived. He said 34 Egyptian supporters of ElBaradei were arrested in Kuwait on Thursday and Friday.
There was no formal comment from Kuwait or Egypt on the arrests and deportations, and the fate of the others arrested was not immediately clear.
Egypt's Muslim Brotherhood, the country's largest opposition movement, called the arrests "an insult."
"The Kuwaiti government has no right to detain these men or to interfere in the affairs of the Egyptian citizens," Hamdi Hassan, an MP affiliated with the banned Islamist group, said in a statement.
Ishak also condemned the deportations and said his group requested a meeting with Kuwait's ambassador to Egypt.
ElBaradei, 67, has emerged as Egypt's most high profile pro-reform leader after retiring from the International Atomic Energy Agency last year.
The Nobel laureate has said he would run for president if constitutional restrictions on independent nominations in next year's presidential elections were changed.
Egypt's President Hosni Mubarak faces mounting opposition at home after almost three decades of rule and has ruled out amending the constitution.
His government has rebuffed foreign calls for reform and dismissed as "unacceptable" a call last week from the US State Department for free elections.
The 81-year-old has not said whether he will run again in 2011, but is widely believed to be grooming his son Gamal as his successor.
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