One of Washington's most influential interest groups is changing its name.

The American Association of Retired Persons said yesterday it has decided it will be known by its acronym, AARP. When pronounced, the name rhymes with harp.

The reason for the change: Too many of the organization's 32.4 million members are still working, said spokeswoman Lisa Davis. The organization, which has been a major lobbying force on issues affecting senior citizens such as Social Security and Medicare, allows individuals as young as 50 to join its ranks.

"Almost one-third of our members are still working," Davis said. So last week, the group's board voted to drop the formal name and retain only the letters AARP.

The group soon will file corporation papers with District officials making the change formal.

It won't affect any of the organization's policies, but it will create a name that Davis said would be "more reflective" of the organization's current members. "It's not as drastic a change as it seems," she said. The group's red-letter AARP logo has been a registered trademark for years.

The name change was confirmed as Fortune magazine honored the group for the second consecutive year as the most powerful interest group in the capital. The ranking was based on the magazine's poll of Capitol Hill staff workers.

The organization, now managed by executive director Horace B. Deets, was founded in 1947 as the National Retired Teachers Association. It evolved in 1958 into AARP, an organization "dedicated to helping older Americans achieve lives of independence, dignity and purpose," and has built membership with the help of computerized mailing lists that identify virtually every American approaching age 50. Membership costs $8 a year.