A 16-year old girl gives birth to an illegitimate son. Without a husband and unwilling to raise the child herself, she places him in an orphanage for adoption.

It is a familiar scenario of a teenage pregnancy, but a scenario that Jeff Claypool could not accept.

When Claypool, a 20-year-old Air Force enlisted man from Severna Park, Md., discovered that his girlfriend had given their child to the Catholic Archdiocese of Washington for adoption, he decided to fight for custody by filling paternity suit.

Although Claypool is named as the father on the child's birth certificate, he is filing the suit to establish his parenthood legally. According to legal experts, the case is highly unusual since most paternity suits are filed against the suspected father.

Claypool won an initial victory in May, when Prince George's County Judge David Ross agreed to hold up the adoption proceedings until his claim is resolved some time this summer.

The Rev. Msgr. James F. Montgomery, director of the Associated Catholic Charities of the Archiocese of Washington, which has custody of the infant, is skeptical of the suit. "I think too many people have seen "Kramer vs. Kramer,'" he says.

Nevertheless, the archdiocese, which places about 30 babies for adoption every year, will wait until the court rules before deciding what to do with the child.

For Claypool, himself an adopted child, the reason for the court battle over his son was simple. "He's the only flesh and blood I know," he says.

Claypool and his girlfriend began dating in 1977 when both were living in Severna Park in Anne Arundel County. When Claypool enlisted in the Air Force in 1979, he was unaware she was pregnant.

Several months later while stationed at Valdosta, Ga., Claypool returned to his barracks to find a letter from his girlfriend saying she had given birth to a boy named Michael.

Claypool excitedly told friends he was a father, but a short time later, another letter arrived, informing him the infant had been put up for adoption.

After phoning the orphanage and being told no information could be released, Claypool resolved to do everything possible to gain custody of the infant.

At first, his adoptive father opposed him. "I thought it wasn't the right thing to do," said Charles Claypool, an Anne Arundel County tractor salesman. "He was in the Air Force: how the heck could he take care of the baby?"

But he changed his mind after visiting his son's military base and getting assurances that the base had adequate facilities for Michael.

Jeff Claypool had been permitted to see Michael several times since the birth under strictly enforced conditions -- no photographs are permitted, and the infant may not be taken home.

Michael's mother is permitted to visit, but Claypool said he does not know if she has.

The mother refused to discuss the "heartache situation," as her father calls it. Her attorney also refused comment on the case but said that as far as he is concerned, there is "no father yet."

Claypool's attorneys filed two lawsuits: the paternity claim in Prince George's, and another lawsuit in the District, where secret adoption proceedings were already under way to place the infant with a new set of parents.

Paternity suits historically have been filed by unmarried mothers who want to establish a father's paternity in order to obtain support for their child. This case exists, Claypool's attorneys say, because the infant's mother simply refuses to give Claypool the child, yet doesn't want it herself. m

The case may have broad ramifications because of the increasing number of unmarried couples living together and producing children. "In these situations, said one adoption law expert, "If a man has no rights, it is not quite right, is it?"

Claypool is convinced the infant knows his father. On his first visit, Michael looked up at him, immeditately grabbed his finger, and, he said, "didn't let go the entire time."

The baby's blond hair and blue eyes, Claypool said, strikingly resembled his own. "I played with him a while," Claypool recalls, "then he fell asleep in my arms and I started to cry."

After the visit, Michael was taken to an undisclosed location that Archdiocese officials refuse to reveal. It is believed that the baby is staying temporarily with foster parents somewhere in the Washington area.

Ironically, Claypool had intended this summer to take legal steps to determine the identity of his own natural parents.

His adoptive mother warned him, however, that his natural mother, if located, may not be receptive to his attempts to find her. But Claypool is convinced she will be pleased, just as he is certain that his son will later be glad to know his natural father.

The efforts to locate his parents however, will have to wait until he has completed his attempts to claim Michael, Claypool said. A hearing is scheduled for later this summer in which Claypool is confident he will win custody of his son.

Then, Claypool says, he will resume the search for his parents.