Several tense confrontations erupted between police and smaller groups of protesters but they were negotiated with no arrests. However, protesters have promised greater disruptions beginning Monday, and police have indicated they won't be as willing to compromise.

''It's a cat and mouse game. It's going to go on all week,'' police Commissioner John Timoney said. ''Today's Unity 2000 march went off overall pretty well. I'm not that naive to think that we'll be that lucky tomorrow.''

For the most part Sunday, there was more of a festival atmosphere with musicians, inspirational speakers, elaborate costumes and floats, and many signs, banners and flags.

The Unity 2000 rally attracted up to 5,000 people to a parade along streets closed by police for the event, Timoney said. Other, less peaceful demonstrations are expected during the four-day convention that begins Monday.

Police, who numbered in the hundreds along the march route, reported few incidents, a contrast to protests last fall in Seattle at the World Trade Organization meetings that drew about 50,000 people and resulted in millions of dollars in property damage.

Minor clashes erupted between anti-abortion and abortion rights activists, including an injury to an abortion rights protester and a shouting match between a police captain and the leader of an anti-abortion group. Tim Troxler, 34, received minor injuries when he fell off a truck with anti-abortion messages on it while he tried to cloak the truck in an abortion rights banner.

Late in the day, about 100 anti-death penalty activists faced off with officers at two locations during a permitted protest for which police closed numerous downtown streets. Both incidents became more heated when hundreds of passers-by surrounded the groups and chanted in support of the activists.

Police said they lost patience with the activists when marchers became uncooperative. More than 400 uniformed officers arrived and blocked the intersection, telling the 75 activists they would be arrested if they did not walk on the sidewalk. After 30 minutes of negotiations, the activists were escorted through the police lines on the sidewalk and the groups dispersed.

Less than an hour later, more than 100 activists sat down in the street in front of the District Attorney's Office a few blocks away. They left after police again threatened arrests.

''We know, when they come forward we back up,'' said activist Heather Saslovsky, 20, of Long Island, N.Y. ''This happens all the time, and it went better than it could have. At least they didn't beat on me.''

There were no march-related arrests reported; officials reported several cases of heat-related illnesses.

The Unity 2000 march included more than 200 groups supporting issues from environmental protection and animal rights to campaign finance reform and an end to police brutality. Two animal-rights activists wore furry pink pig and yellow chick costumes, while about 30 mock ''Billionaires for Bush and Gore'' wore tuxedos and evening gowns.

After Sunday's parade, protesters held an afternoon rally near the Philadelphia Museum of Art. Among the speakers were national AFL-CIO President John Sweeney and National Organization of Women Executive Director Patricia Ireland.

While Sunday's march had been billed as a peaceful rally, police were bracing for trouble once the convention begins. A homeless march, which did not receive a city permit, is scheduled for Monday. Activists also have said they will stage various acts of civil disobedience Tuesday.