A new test, followed by drug treatment, could help hundreds of thousands of infertile men and women have children.

The technique has been fully applied to only four persons -- three men and one woman -- so far. But in just one month the woman became pregnant, and one of the men succeeded in making his wife pregnant.

The condition that was successfully treated may afflict as many as 5 to 10 percent of all the infertile.

The provocative results are reported in the New England Journal of Medicine today by University of Pennsylvania doctors.

Dr. Gilbert Haas Jr. and coworkers first developed a test to identify those men and women who are infertile because for some unknown reason they produce antibodies, the body's disease-fighting agents, against sperm. These women produce antibodies that kill their husbands' sperm. The men produce antibodies that kill their own sperm.

Other doctors have tried to identify men and women who produce such antibodies, but results had been inconclusive. And some doctors. Haas says, began to doubt "whether antibody mediated infertility was really a problem" or even existed.

Haas gave his new test to 614 infertile people, including 257 couples. He determined that 10 percent -- 13 percent of the women and 7 percent of the men -- did produce sperm-killing antibodies.

The 614 persons studied might not be an accurate cross-section of all infertile men and women, Haas concedes. Still, he says, it is probable that at least 5 percent of the infertile suffer from thesame problem.

Haas gave corticosteroids -- cortisone-like drugs -- to try to suppress the unwanted sperm-fighting antibodies temporarily. This, too. had been tried before, but the problem had been to identify those who could be helped.

Haas essentially mixed blood from his infertile patients with sperm from healthy, normal men. He then determined whether antibodies in the blood attacked the normal sperm.

Now, Haas maintains, this "objective" test may be used to find the many suseptibles and then help manage their "antibody infertility."