The protesters want Mr Musharraf's actions overturned.
"The lawyers' representative body has called for this march against the atrocious acts of Pervez Musharraf on 3 November 2007 and they are demanding unconditional reversal," Athar Minallah, a spokesman for Mr Chaudhry, told the BBC.
The convoys will then head for Islamabad, making several stops on the way where reception camps have been set up to receive them, offer them drinks and shower rose petals on them.
The BBC's Syed Shoaib Hasan in Islamabad says the rally could be the first real challenge to Pakistan's fragile new civilian government.
It could also increase tensions in the government as the junior partner, the Pakistan Muslim League of former Prime Minister Nawaz Sharif (PML-N), is taking part in the demonstrations.
On Monday, about 4,000 activists from various political parties gathered in Karachi and chanted slogans such as "Go, Musharraf, Go!" and "Musharraf is an American dog!"
Security forces were also out in large numbers, but the rally was peaceful.
Lawyers at a similar protest outside the Multan District Courts hung a large effigy of President Musharraf before beating it and setting it on fire.
The president dismissed dozens of judges, including the Supreme Court chief justice, in November when he imposed emergency rule. At the time he faced numerous legal challenges to staying on as president.
Supporters of the lawyers say it will be a 'historic' protest
The move further enraged lawyers and his political opponents, who were already infuriated over his attempts earlier in the year to sack Mr Chaudhry.
After they won the elections, both the Pakistan People's Party (PPP) and the PML-N promised to restore the judges but they have not agreed on the mechanics of how this should be done.
The PML-N argues that the judges should be reappointed by an executive order from the prime minister.
But correspondents say that the PPP wants to link any reinstatement to a major package of constitutional reforms.
The two parties also appear to differ over how to deal with President Musharraf.
PML-N leader Nawaz Sharif has called for his removal and trial for treason, but the PPP appears wary of a confrontation with the president, who has insisted that he has no plans to resign.
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