WASHINGTON — Retired Vice Adm. James Stockdale, a former prisoner of war and Ross Perot's running mate in 1992, has died, the Navy announced yesterday. He was 81.

The Navy did not provide a cause of death but said he was suffering from Alzheimer's disease. He died at his home in Coronado, Calif.

In the 1992 presidential election, Adm. Stockdale became independent candidate Perot's vice- presidential running mate, initially as a stand-in but later as the candidate.

Adm. Stockdale gave a stumbling performance in the nationally televised vice-presidential debate against Dan Quayle and Al Gore and later said he didn't feel comfortable in the public eye.

During the debate, he commented on an exchange between Quayle and Gore: "I think America is seeing right now the reason this nation is in gridlock. The trickle-downs and the tax-and-spends, or whatever you want to call them, are at swords point."

When Perot ran again in 1996 as the candidate of his Reform Party, Adm. Stockdale had rejoined the Republican Party.

Adm. Stockdale was born in Abingdon, Ill., and graduated from the U.S. Naval Academy in 1947.

During the Vietnam War, he was a Navy fighter pilot based on the USS Oriskany and flew 201 missions before he was shot down on Sept. 9, 1965. He was the highest-ranking naval officer captured during the war, the Navy said.

He endured more than 7 ½ years as a prisoner, spending four in solitary confinement, before his release in 1973. He was tortured repeatedly, the Navy said.

Adm. Stockdale received 26 combat decorations, including the Medal of Honor, the nation's highest medal for valor, in 1976.

Survivors include his wife, Sybil, and four sons.