Dianne H. Pilgrim, director of the Smithsonian Institution's Cooper-Hewitt National Design Museum in New York, has announced her intention to resign after 11 years in the post.

Pilgrim, 58, will continue to serve the museum as director emeritus and senior adviser for special projects after a six-month leave commencing Jan. 3. "I just think that it is time," Pilgrim said yesterday. "I would really like to get back to my first love, which is curatorial work and research."

Expressing his regret at her resignation, Smithsonian Secretary I. Michael Heyman noted that Pilgrim "has done a wonderful job," and said her continued "advice and counsel will be invaluable" to the museum. Heyman is expected to appoint an acting director in the next few weeks to serve while the institution conducts a search for a new permanent director.

Pilgrim, formerly curator of decorative arts at the Brooklyn Museum, is the second director of the museum since it was taken over by the Smithsonian in 1968. During her tenure the museum completed a $20 million renovation of the former Andrew Carnegie Mansion and adjacent properties on Fifth Avenue, providing better exhibition, storage and research spaces for the priceless 250,000-item collection.

In 1994 she engineered a subtle but important change in the institution's name--instead of the Museum of Design it became the Design Museum. The new name, she said, is "active, not passive--design is both a verb and a noun."

As part of her activist philosophy, Pilgrim instituted the National Design Awards, the first series of which will be distributed next fall, and a triennial survey of American design scheduled to be unveiled for the first time in March.

Pilgrim's effort to significantly increase the New York museum's presence in Washington, however, was unsuccessful. Two exhibitions initiated by the Cooper-Hewitt have been transported to the Mall, but no space dedicated to Cooper-Hewitt shows in Washington was ever found. "The problem, in a word, was money," she said.

Pilgrim, afflicted with multiple sclerosis since 1978, runs the museum from her wheelchair. Not surprisingly, access for the handicapped to the museum's buildings and collections improved dramatically during her administration. Health did not play a role in her decision to resign, she said yesterday.

CAPTION: Pilgrim has headed the New York museum 11 years.