Hundreds of thousands of homosexual men and women yesterday marched up Fifth Avenue in New York, Market Street in San Francisco and in Chicago and Miami to observe the 10th anniversary of an incident many say was the start of the nationwide gay rights movement.

The marches commemorated the Stonewall Riot June 28, 1969, in New York, thought by many to be the beginning of the gay rights movement.

In San Francisco, nearly 250,000 homosexuals walked to a rally at the Civic Center plaza - the scene of last month's bloody confrontation between homosexualrights supporters and police after former city supervisor Dan White was found guilty of manslaughter in the shooting deaths of Mayor George Muscone and Harvey Milk, the city's first avowed homosexual supervisor. The protestors felt he should have been convicted of a more serious charge.

Memories of the battle were evident yesterday. Demonstrators carried signs proclaiming "No more Dan Whites" and "We Remember You, Harvey."

Organizers of yesterday's march, fearing a repeat of the violence, trained hundreds of volunteers in nonviolent monitoring techniques. There were rumors of a so-called "blue fly," or police sick-out, but a police spokesman said it did not materialize, and about 400 uniformed officers were on hand for the parade, including more than 100 riot control officers.

In New York, demonstrators from across the Eastern Seaboard assembled at Sheridan Square in Greenwich Village and marched to Central Park for a rally. The marchers, sometimes is abreast, formed a line 10 blocks long.

the incident in Greenwich Village 10 years ago that yesterday's march commemorated was at the Stonewall Inn, where police raided a bar patronized by homosexuals. An angry group of bar customers resisted arrest, set a small fire and threw objects, including a parking meter, at officers.

The group claimed police had repeatedly harassed them at the bar because they were gay. Ten persons were arrested and seven officers were injured.

Seth Lawrence, co-chairman of the Christopher Street Liberation Gay Committee, an umbrella group for homosexual organizations in New York, said yesterday's march was intended to help boost efforts to get a bill passed by the City Council to prohibit discrimination against homosexuals in housing, employment and public accommodations.

"I am exhilarated," he said, looking at the crowd at Sheridan Square. "Lesbians and gay men in New York City are realizing that no one is going to look out for our family but us."

Ed Marcus, who carried the committee's banner, said homosexuals were subject to political, economic and psychological repression as well as physical attack. He said there was "a conspiracy of silence, of keeping us invisible."

That's why it's important to have lesbian and gay teachers," he added.

A group of about 11 persons maintained a vigil outside St. Patrick's Cathedral on Fifth Avenue Saturday night.Yesterday they handed out leaflets to church goers, calling for an end of opposition by the Archdiocese of New York to the proposed gay rights bill.

In Chicago, about 4,000 homosexual men and women marched or rode in cars and floats yesterday in a celebration of Gay Pride Day. In Florida, where two homosexual rights ordinances have been struck down by voters, about 2,000 men and women, many fearful of being identified by the news media, marched peacefully in downtown Miami.

Despite the large turnout for marches yesterday, a planned march on Washington, D.C., in October appears to be in doubt.

An organizer of the San Francisco parade laughed at the mention of it: "That's an effort plagued by much greater difficulties than the San Francisco parade committee. It's something that takes a lot of money and thought, but it's just before an election here so the mainstream people won't be involved. That leaves it to a pretty small group of people without much political sophistication."