A growing protest that has forced the D.C. police department to "streamline" its arrest procedures continued yesterday when 87 antiapartheid demonstrators were arrested at the South African Embassy, the largest number of arrests there since the ongoing embassy protests began nine weeks ago.

Yesterday's demonstrators, most of them from labor unions, stood on the snowy sidewalk in front of the embassy's Massachusetts Avenue NW complex and hurled chants of "Free South Africa" before being led away in plastic "flexcuffs" to a waiting police van and eight paddy wagons. They were taken the 2nd and 3rd District stations.

D.C. Del. Walter E. Fauntroy, a cochairman of the Free South Africa Movement, called the demonstration "a gift of conscience" from the labor movement and the group's own "preinaugural message" for Ronald Reagan.

"This is the largest number to make an approach to the embassy to date," said Fauntroy. He vowed that protesters "will continue to show up here each day of each week of each month" until the South African and U.S. governments adopt policies that improve the lot of black South Africans.

The weekday afternoon demonstrations, for which supporters have volunteered to be arrested through February, have focused attention on the racial segregationist rule of South Africa and on U.S. diplomatic and business ties there.

Yet for some police officers, the daily, well-orchestrated protest is, in the words of one police official, "getting to be a pain in the neck."

So far, according to police officials, the demonstration has not caused a drain on budget or personnel. And police are quick to note that the demonstrations have been conducted by a peaceful, "controllable group that doesn't pose a threat."

But the arrests, which began Nov. 21 with three and are expected to climb to 150 or more by next Friday, have created extra paper work and required the shifting of more officers and transport vehicles to the embassy.

To handle the growing number of arrests, police here have begun simpler "field arrest" procedures commonly used for mass demonstrations associated with antiwar protests of the 1960s.

Instead of filling out individual prosecution forms for each person arrested, police say they have -- with the approval of the U.S. attorney's office -- prepared two standard forms, one for men and one for women, that give the charge and a narrative of the circumstances leading to the arrest. The list of names of those arrested each day at the embassy is then attached to the form.

"Administratively, we have spent more time processing 100 people . . . . There's more paper work," said Isaac Fulwood, assistant chief for field operations. "But this has been going on for a while now, and we have fallen into a good pattern and a good routine."

Once taken into police custody, demonstrators have three choices: they can spend the night in jail and appear in court the next available day; they can post bond and appear in court the next available day; or they can be released on citation, which requires a court appearance within two weeks. The citation option, however, is not available to those who have outstanding arrest warrants or who are considered a threat.

Many demonstrators arrested in the early weeks of the embassy protest elected to spend the night in jail. But police say the vast majority are now taking the citation, particularly since the U.S. attorney's office has dropped charges against the protesters, saying their prosecution would further clog the court system.

Taking the citation also simplifies police work, since those who spend the night in jail must be fingerprinted and photographed. For those being released, police just take the right thumbprint and no mug shot.

Police officers from the department's 285-employe Special Operations Division have been handling the demonstration at the embassy site, but other districts may have to be involved if arrest numbers rise, police say. Another concern is the availability of transport vehicles, particularly paddy wagons used for violent suspects who might tear up a police cruiser.

Police say they have not been caught short yet, but they worry that it could happen. The worry is aggravated because the District is under court order to process all suspects and get them in the cellblock within three hours.

Despite such misgivings, demonstrators reported yesterday they were well treated by officers. They said they engaged in "friendly banter" with police and were allowed into the snack bar area to buy sodas and candy while waiting to be processed. There were some complaints about being handcuffed too tightly, however.

"We have not had the smallest expression of irritation from the police department," said Randall Robinson, coordinator of the demonstrations, who described police as being "sympathetic" as individuals to the protest's aims. "We have tried to make their job no harder than it has to be."

Robinson criticized the U.S. attorney's decision to drop charges against the demonstrators, saying that police are doing their jobs.

"These are violations of the law, and they have no choice but to make arrests," he said.