Gillian Anderson, best known to American audiences as Agent Dana Scully of the F.B.I., from the Fox television show “The X-Files,” will be one of the new hosts of “Masterpiece Theater” on PBS when it begins its new season on Jan. 13, the program’s producers plan to announce today.

Naming Ms. Anderson as a host is part of a broad overhaul of the look and scheduling of “Masterpiece Theater,” now 37 years old, intended to bring in more viewers by getting rid of some of the packaging that Rebecca Eaton, the program’s executive producer, said was beginning to look antiquated. Among other changes, the series, which won three Emmy Awards this year, will group films by genre, separating the period works from the contemporary dramas.

Ms. Anderson will introduce the January-to-May block of costume dramas that are to be known as “Masterpiece Classic.” They will begin this season with adaptations of six Jane Austen novels. Additional hosts will be chosen to introduce summer programming under the rubric “Masterpiece Mystery!” and the fall block of dramas, to be known as “Masterpiece Contemporary.”

Even the familiar opening music — Jean-Joseph Mouret’s brass fanfare “Rondeau” — won’t be spared. It will be heard only in snippets in the new opening.

In another change the producers have begun negotiating for Internet streaming rights to the films they acquire; this season some of them will be available streamed online for the first time, and on video on demand.

“After 37 years I decided we should take a good hard look at how ‘Masterpiece Theater’ was coming across to the public,” Ms. Eaton said. What emerged from research, she said, was that “the caliber of the programming is not what should be changed but perhaps the on-air look and presentation and scheduling of the programming.”

Taking pains to reassure the series’s passionate fans, who research showed were among the most loyal donors to public television stations, Ms. Eaton said: “We’re not tarting it up or dumbing it down. We’re making it as easy as possible to find and get into the programs.”

“Masterpiece Theater” is one of the higher rated PBS programs. John Boland, the chief content officer for PBS, said the extensive audience research showed that viewers singled it out as one of six programs that defined public television for them. With that in mind, PBS and the Corporation for Public Broadcasting allocated extra money for the overhaul and promotion of the series this season. “Every jewel needs a little polishing now and then,” Mr. Boland said.

While the goal is to attract more viewers, he said “the relaunch certainly can’t hurt” efforts by PBS to find a new corporate sponsor for the program, which has been without underwriting since 2004 when ExxonMobil ended its support of about $9 million annually. Even without a sponsor PBS is “committed to ‘Masterpiece Theater’ for the long term,” Mr. Boland said.

The choice of the 39-year-old Ms. Anderson as host is a significant change from the previous two occupants of the job, both of whom were male journalists: the British-born Alistair Cooke, who introduced the program from 1971 until 1992, and his successor, Russell Baker, the former columnist for The New York Times.

The program has been without a host since Mr. Baker stepped down in 2004. Ms. Anderson is also “considerably younger than either of our previous hosts,” Ms. Eaton said, adding that Ms. Anderson would be alone in a studio, not sitting in the show’s familiar book-lined study. Ms. Anderson, who lives in London and is about to start shooting an “X-Files” film sequel, is already familiar to “Masterpiece” viewers, having starred as Lady Dedlock in Charles Dickens’s “Bleak House,” shown on PBS in January 2006.

In addition to the Austen films, which will begin with a new adaptation of “Persuasion,” starring the British actress Sally Hawkins, the season includes “Miss Austen Regrets,” a biography of the novelist. Other films include “Cranford,” a three-part mini-series starring Judi Dench; “My Boy Jack,” starring Daniel Radcliffe, of the Harry Potter movies, playing the son of the author Rudyard Kipling; and a new adaptation of E. M. Forster’s “Room With a View.”