The National Institutes of Health, it seems, has no interest in being in the monkey business -- at least when it comes to these particular monkeys. The scientist-owners of the animals have no use for them either, judging by one of their letters to the government. Indeed, each side has tried unsuccessfully to hand off the monkeys to the other.

Enter the animal welfare advocates, who started the fracas five years ago when the monkeys were seized in a celebrated raid at a Silver Spring laboratory. The advocates want to send them to a veritable monkey paradise in Texas.

The trouble is neither NIH nor the owners will give them up. So everyone, represented by high-priced lawyers and armed with hundreds of pages of legal documents, is fighting it out in federal court.

Last week Congress got in on the act, as more than 100 members signed a letter to NIH branding the confinement of the 15 animals "in small steel cages" at the cost of $30,000 a year both "inhumane" and a "waste of taxpayers' dollars."

Nearly 70 scientific and academic organizations have joined the fray on NIH's side, fearing, according to one of their spokesmen, many such suits if the court rules for the animal groups.

For their part, the animal groups, frustrated with the drawn-out court fight that has cost them more than $200,000, plan to start a vigil on the NIH campus in Bethesda tomorrow and remain there, their leader promises, "until the monkeys are freed." That, according to NIH official William F. Raub, is unlikely to happen until the court case on this "important issue" has been decided.

The battle over the monkeys, both in and out of court, has attracted national attention as it pitted the animal welfare movement, whose members believe that animals are among society's most exploited and least understood victims, against the formidable research community, which sees the case as a threat to its most valuable resource, the research animal.

New York writer and animal advocate Cleveland Amory has declared the case "the Armageddon of the laboratory movement . . . . It could set a precedent to get animals out of laboratories legally."

The tug-of-war began in September 1981 when the Montgomery County police, relying on evidence gathered by animal rights advocate Alex Pacheco, seized the animals in a raid on the lab at the Institute for Behavioral Research in Silver Spring. Police charged the chief researcher, Edward Taub, with animal cruelty, alleging that monkeys had unbandaged open wounds, lived in filthy cages and at times went without food or water.

Taub, who denied mistreating the animals, was convicted on one count of animal cruelty. The conviction was overturned in 1983 by Maryland's highest court, which ruled that the state's anticruelty statute could not be applied to federally-funded research projects. Taub's project was funded by NIH.

Meanwhile, the court gave the monkeys to NIH for temporary care at a Poolesville facility. In December 1981, Pacheco's group, People for the Ethical Treatment of Animals, and like-minded groups filed a lawsuit to block return of the 15 monkeys to the institute.

The federal court in Baltimore dismissed the case, finding that the animal groups had no "legal standing" to bring the suit on the animals' behalf. The groups have appealed and are set to argue May 8 before the 4th U.S. Circuit Court of Appeals in Richmond.

According to the animal rights groups' lawyer, Edward L. Genn, they believe NIH has a "right to declare the animals their own" because they were bought with federal money under a grant terminated because the institute and Taub violated procedures for proper care.

However, according to NIH's Raub, the monkeys are the institute's property. He said it wants them to "remain available for an appropriate institution to complete the study for which they were acquired." Taub's study dealt with the effects of damage to the nervous system.

NIH cannot take "unilateral action" to move the animals anywhere because "they are not our property," Raub said. Such a move could be considered an act of "bad faith" while the case is in court, he added.

In a letter to Raub, the institute's chief executive officer said he had no interest in having the monkeys returned. "The trustees' objective is to relinquish ownership of the primates without publicity," said Joseph Vasapoli in a September 1985 letter.

Pacheco recently led a band of visitors to see the monkeys. He rubbed the furry face of "Billy," whose arms were paralyzed in research, and fed a dish of bakery-bought cookies to "Sara," the friskiest of the bunch. And he talked about the animal sanctuary in the hills of Texas owned by a group called Primarily Primates where he would like to see them live out their lives.

"These animals are a symbol," he said later. "This is the only time a whole colony of lab animals has survived. They have defied the system."