True North owns 45 percent of Modem Media, an Internet services agency, but wants to sell the stake.
The on-line portion of the account remains at Modem Media.
Two of the six agencies are owned by True North Communications: Modem Media.
The acquisition of Vivid, which has about 100 employees, is meant to help Modem Media.
It will be the third deal in recent months for Modem Media.
The third partner in Modem Media, Robert Allen, 29, will become Modem's president, also a new post.
Modem Media opened in 1987 as a so-called electronic direct marketing agency.
Other agencies working for E*Trade include Modem Media.
The merged agency will be headed principally by executives of Modem Media.
True North will own 70 percent of Modem Media.