Over seven decades, Ms. Hagen acted in Shakespeare, Chekhov and Shaw, as well as in plays by Mr. Albee and Tennessee Williams. With her husband Herbert Berghof (who died in 1990), she ran the HB Studios in Manhattan and was celebrated not only as an actress but also as a teacher of acting and author of books on the subject. She continued to teach after a stroke and until several months before her death. Occasionally she appeared in films and on television, but principally her life was onstage, and it was there that she was able to incarnate the widest diversity of characters.

Ms. Hagen made her professional debut in 1937 playing Ophelia to Eva Le Gallienne's Hamlet, and was acclaimed for her Nina (in ''The Seagull''), Desdemona (opposite Paul Robeson's Othello), Shaw's St. Joan, Blanche DuBois in ''A Streetcar Named Desire'' and as the title character in ''The Country Girl'' by Clifford Odets. Mr. Albee's Martha became her signature role.

It was a long journey from Ophelia to Martha, but one that she traveled with an unmatchable authority and an intuitive sense of character. Whether she was playing a saint or a termagant, she anchored each role with a firm base in reality. Despite her onstage strength, she said she always considered herself ''a vulnerable actress.'' Once asked what qualities an actress needed to play Martha, Ms. Hagen said, ''Intelligence, voluptuousness and hypersensitivity,'' and then added, ''wit'' -- all of which she had in abundance.

In 1999, she called her whole goal as an actress ''the spontaneity that comes without planning.'' Whenever possible, she uncovered the drama behind the comedy -- or the comedy behind the drama. As she said, ''Somebody with wit and a sense of humor sees the most tragic event without the sentimentality, sees in any life experience something ludicrous -- which is probably why Chekhov is my favorite.''

She believed a performance should change in the course of the run, depending on the identity of the other actors, the audience response and the actress's mood and temperament. She played Blanche opposite Marlon Brando, Anthony Quinn (her favorite), Ralph Meeker, Richard Kiley and Jack Palance. ''If you go on with another actor and your performance doesn't change, you're a bad actor.''

In contrast to many other actors, she loved long runs: ''After a couple of months,'' she said, ''it really starts to get in my bones.'' On keeping a part alive, she called Laurette Taylor her guide. She saw her play Amanda in ''The Glass Menagerie'' 10 times, saying, ''Ten different exciting performances -- to me, that is the magic of the theater.''
She studied briefly at the Royal Academy of Dramatic Art in London, and at the University of Wisconsin, and left college -- and left home -- to pursue an acting career.

In 1937, Le Gallienne was preparing to play Hamlet in a production in Dennis, Mass., and was having difficulty finding an Ophelia. Ms. Hagen sent a letter requesting an audition. As Le Gallienne recalled in her autobiography, her impulse was to refuse, but something in the letter encouraged her to invite the young actress to audition.

''She was very young -- only just 17 -- a tall, rather gawky creature, by no means pretty, but with a face that one remembered,'' Le Gallienne wrote, adding she had ''the shy ungainly grace of a young colt.'' For her audition, Ms. Hagen acted the end of the trial scene from ''St. Joan,'' ''quite badly,'' Le Gallienne said, ''and yet I sensed in her an inner truth that very occasionally filtered through in a word or a look.'' She told her to go and think about the role and return in an hour.

''The improvement was startling,'' Le Gallienne said, ''The truth that had glimmered so faintly in the first reading now blazed up strongly, and the overall effect was strangely moving.'' She cast her.

In the dress rehearsal, she said, ''the sacred fire struck, and the child Uta was transported to a region which I well knew she would no