Fox, which unveiled its fall lineup on Thursday, also will air three new dramas and a new sitcom.

UPN also announced a schedule notably for its acquisition of Star Trek: Enterprise and the pairing of former WB shows Buffy the Vampire Slayer and Roswell on Tuesdays.

Here's a look at Fox's fall lineup:

Fox's Sunday lineup will remain intact, with comedies Futurama, King of the Hill, The Simpsons and Malcolm in the Middle leading into The X-Files at 9 p.m. After appearing in only a handful of this season's shows, The X-Files' David Duchovny will not return in the fall as FBI agent Fox Mulder.

"I guess he thinks it's time to get on with his life," said Sandy Grushow, president of Fox Television Entertainment Group, Reuters reported.

Duchovny's agent, Risa Shapiro, would not comment.

Mondays will remain David E. Kelley drama night, with Boston Public and Ally McBeal. It is not yet known whether Robert Downey Jr., whose final appearance this season on Ally McBeal boosted the show's ratings, will return follow the resolution of his legal and drug-related problems. The new 20th Century Fox drama Emma Brody will air in the midseason in lieu of Ally McBeal reruns.

Tuesdays will lead with the sitcom That '70s Show, followed by the new DreamWorks sitcom Undeclared, a college kids ensemble, and the new 20th Century Fox/ Imagine Television drama 24.

Wednesday nights will be entirely devoted to sitcoms, starting off with reruns of The Simpson, That '70s Show and Malcolm in the Middle. The second season of the family show Grounded for Life will air at 8:30 p.m., followed by the third season of Titus at 9 p.m. The new 20th Century Fox/ Regency TV newcomer The Bernie Mac Show will close the night's prime-time programming.

On Thursday, Fox will place its animated comedies Family Guy and The Tick at 8 p.m. and 8:30 p.m. respectively, competing against NBC's Friends and CBS's Survivor. Temptation Island 2 will air at 9 p.m.

Fridays will now be the Dark Angel night, which relocates from Tuesday, followed by the new Diane Keaton-directed drama Pasadena, a nighttime soap about the trials and tribulations of a wealthy family in the media business.

Saturdays will remain bad-boy nights, with Cops and America's Most Wanted staying in the same timeslots. MADtv will return at 11 p.m.

UPN has picked up two WB dramas for its fall 2001 season, the alien teen sci-fi drama Roswell and Buffy the Vampire Slayer, after much debate.

The network will say farewell to its first successful Monday night comedy series, Moesha, after six seasons. The Hughleys will replace Moesha at 8 p.m. A new show about a sportscaster's relationship with his teen-age daughter, One on One will take the 8:30 p.m. slot, followed by the Moesha spin-off, The Parkers, and Girlfriends, at 9 p.m. and 9:30 p.m., respectively.

Tuesday nights will belong to Buffy and Roswell. UPN stole Buffy away from the WB and rescued Roswell after it was canceled by the WB.

Wednesdays will feature Special Unit 2. The eagerly awaited Star Trek: Enterprise, with Scott Bakula at the helm, closes the night at 9 p.m. Thursdays will carry the excitement of WWF Smackdown!, with a two-hour dose of the ready-to-rumble extravaganza. Fridays will become UPN's movie night.