Soviet Defense Minister Dmitri Ustinov failed to appear at the annual military parade in Red Square today, giving rise to speculation that the 76-year-old Politburo member, one of the most powerful men in the Soviet Union, is ailing.

As is the custom, Ustinov had been scheduled to ride past the troops in an open limousine and give the traditional speech on the 67th anniversary of the 1917 revolution.

Instead, his role was filled by Marshal Sergei Sokolov, 73, one of three deputy defense ministers whose stand-in performance today points to him as a possible successor to Ustinov.

After the parade, Politburo member Viktor Grishin told a correspondent for Cable News Network that Ustinov had a "sore throat." A Foreign Ministry spokesman said he "understood Ustinov is unwell."

Ustinov has not been seen in public since Sept. 27, and on Oct. 31 he was not present at the airport to greet Indian Defense Minister S.B. Chaban. On that occasion, Sokolov headed the delegation, outranking Marshal Sergei Akhromeyev, who has been chief of the general staff since September.

Sokolov has greater seniority, but when Marshal Nikolai Ogarkov -- since demoted -- held the post of chief of staff, he clearly held the second ranking position in the military after Ustinov.

An announcement, issued Oct. 25, appeared in the press here Nov. 4 saying that Ustinov would "receive" the military parade, as he has done every year since becoming defense minister in 1976.

Ustinov also was absent last night at a Kremlin rally, another requisite function for Politburo members and less strenous than today's military review.

It was the second time in two years that the Nov. 7 display of Soviet military might was marred by the absence of a key figure.

Last year, then-Soviet president Yuri Andropov missed the event, the first time the ceremonies honoring the Soviet revolution took place in the absence of a head of state. Andropov died three months later.

In 1982, then-president Leonid Brezhnev was at the ceremony; he died three days later. That he came, despite his failing health, was reflects the symbolic and solemn importance attached to the Red Square event.

Today, the parade took place under lead-gray skies, without snow. Red Square provided the color, mostly red. Huge posters of workers, students and farmers hung on the sides of the gaint GUM department store, on either side of a giant portrait of Lenin. Red lights lit up the dates "1917" and "1984."

Opposite, on the Lenin Mausoleum members of the Politburo and ranking members of the military stood throughout the two-hour parade. the line-up indicated no shift in the power balance, with Mikhail Gorbachev, the second man in the Communist Party, in a prominent position near Soviet President Konstantin Chernenko.

As the Kremlin clock struck 10, the ceremony began with a review of the troops by Sokolov and Peter Luswev, commander of the Moscow garrison, each standing at salute in twin gray Zil convertible limousines.

In his speech, Sokolov accused "ruling circles of the United States and of the NATO bloc" of heightening world tensions and vowed that the Soviet Union would continue to keep its defense capacity "at a high level."

The parade itself began with thousands of troops -- the Navy in black, the Army in gray and red, paratroopers with blue berets, border guards in green -- marching in rows of 20, in perfect step, in perfect alignment. As the first troops filed past the mausoleum, others waited behind, marching in step, their heavy woolen coats flapping at their knees.

After the troops came the hardware -- 12 antitank missiles, 21 armored personnel carriers, 25 T72 tanks, 8 Frog-7 missiles, in all 15 categories of weapons, rumbling over the Red Square cobblestones in clouds of exhaust fumes.

As had been expected, no new weapons were put on display today, although western military experts are now certain that what they last year called the T80 tank is in fact a T72. The new T80 tank exists, they say, but they have not seen it.

The final hour of the parade was given over to tens of thousands of citizens pouring through the square, carrying flowers made of paper and foam rubber and balloons; many pushed giant posters on rolling trolleys. Voices on a loudspeaker -- one male, one female -- alternated in reading the 63 official Communist Party slogans issued this year.

The signs ran the gamut, a picture of an Uncle Sam with Ronald Reagan's face rising like a rocket from the White House, to portraits of Politburo members, Lenin, Marx and Engels, to copies of newspapers with Chernenko's speeches and interviews, to announcements of local economic achievements, such as the Red Rose factory being 31 million roubles "over plan."

Earlier in the morning, the marchers filed down Gorki Street, with the look of people, earnestly but unenthusiastically fulfilling a duty.

Last night, as the national three-day holiday began, Moscow was lit up from end to end. Acres of red flags lined the streets and bridges, hanging down the sides of buildings. Lighted red stars, hammers and sickles were strung from lampposts.

Yesterday, the streets were filled as people left work early to stock up for the holiday, amid complaints that stores were running out of key items.