Bratt Pack

Benjamin Bratt, who plays Det. Rey Curtis on NBC's ''Law & Order'' and Julia Roberts' boyfriend in real life, is exiting the hit drama at the end of this, his fourth season, according to Studios USA, which produces the show for NBC. He will be replaced by Jesse L. Martin, who is best known as Ally McBeal's on-again-off-again doctor boyfriend. Martin, 28, who guested on last week's ''X-Files,'' was an original cast member of the acclaimed play ''Rent.''

Bratt, 35, whose film credits include ''Clear and Present Danger,'' ''The River Wild,'' and ''Demolition Man,'' is the latest cast member to exit the revolving door that is ''Law and Order.'' Others who have come and gone include Chris Noth, Michael Moriarty, Paul Sorvino, Carrie Lowell, Jill Hennessy, George Dzundza, and Richard Brooks. Interestingly, ''Law and Order,'' which will celebrate its 200th episode next Wednesday, has proven to be immune to ratings drops from the constant cast shufflings. In fact, the show's ratings this season are on the rise, averaging 13.6 million viewers a week. NBC has renewed the show through the 2001-2002 TV season.