In a protean architectural career spanning five decades, Frank Gehry has gone from big time to adventurous obscurity and back to big time again. In the process, he has altered the way many Americans think about modern architecture.

Gehry, 70, was born in Toronto, where he worked part time in his grandfather's hardware store, stocking shelves with nails, saws, pliers, pipe, fencing and so on--an experience possibly predictive of his mature fascination with the nature of all types of building materials, from the everyday to the highly unusual.

The family immigrated to Los Angeles shortly after World War II. Gehry studied architecture at the University of Southern California and did some of his first architectural work for the U.S. Army when, as a drafted clerk-typist, he was put to work designing enlisted men's day rooms. He changed his name from Goldberg in the early '50s, an act he later said he regretted.

Gehry's first full-time job was with Victor Gruen Associates, a postwar pioneer in shopping center design. After leaving Gruen in 1962, Gehry spent much of the next two decades designing large-scale, mainstream modernist projects for the Rouse Co., including the Merriweather Post Pavilion and the Rouse headquarters in Columbia.

In the late '70s, however, Gehry turned his full attention to the more venturesome small-scale projects he had been working on as a creative sideline--houses for artist friends and in-the-know Angelenos and, most notably, a radical remodeling of his own bungalow in Santa Monica. For many of these low-budget projects, he used the most ordinary materials--such as exposed plywood or chain-link fencing--in extraordinary ways.

As the size of his commissions decreased--along with his income--Gehry's reputation for artistic innovation gradually spread. By the mid-'80s, he was beginning to snare large commissions again.

In 1984, for example, he designed a new complex for the Loyola School of Law in downtown Los Angeles, just a few blocks from the small apartment his family had rented after arriving from Toronto in 1947. And in 1988 he was awarded the city's most prestigious cultural commission of the late 20th century--the still-unbuilt Disney Concert Hall. In 1989 he received the coveted international Pritzker Architecture Prize.

From the Disney hall design until now, Gehry's worldwide projects have demonstrated an increasing geometric freedom and complexity. In part, this is simply an elaboration of a longtime aesthetic interest in complicated, yet functional, three-dimensional forms. And in part it is super-sophisticated computer technology that now enables Gehry to translate his complex conceptions into reality.

Gehry's most famous building--the titanium-sheathed 1997 Guggenheim Museum in Bilbao, Spain--appears like a gleaming, improbably shaped ship in a rough, untidy harbor. Although many of his other projects are more sedate, all--from the Vitra furniture and design museum in southern Germany to the University of Toledo Center for Visual Arts in Toledo, Ohio--retain an element of formal surprise.

CAPTION: Frank Gehry's Nationale-Nederlanden Building in Prague: A designer with a reputation for artistic innovation.