On May 22, 1989, doctors at the National Cancer Institute in Bethesda, Md., hovered over the bedside of their patient, a 52-year-old man dying of cancer. A nurse hooked up a plastic intravenous bag containing a milky fluid.

The man and his wife held hands. The IV dripped. The minutes ticked by.

It was a critical moment in science's long march toward gene therapy, which seeks to cure disease by altering the molecular instructions for life.

For the first time, genes were being transplanted into a human being. If the genes worked, medical science would never be the same.

Dripping into the IV were the man's own white blood cells, which had been removed from his tumors and supercharged in the lab to increase their cancer-fighting power a million-fold. Spliced into these cells were bacterial genes that would serve as tracer bullets to see if the cells were finding their targets.

Even though the genes would play only a passive role in the cancer treatment, nobody knew with certainty what would happen when alien genes were introduced into a person. They might even kill him.

However, the blood-cell therapy represented the man's last hope. All other efforts had failed to arrest the black-mole cancer-malignant melanoma-that had spread uncontrollably throughout his body.

The man's doctor, NCI chief of surgery Steven A. Rosenberg, projected the upbeat confidence he had displayed as Ronald Reagan`s surgeon during the former president's bouts with colon cancer.

"Today is the first ever!" he declared jubilantly for posterity, in honor of the gene transfer.

But Rosenberg`s partner at the National Institutes of Health, gene splicer Dr. W. French Anderson, was less self-assured. He had been dreaming about this morning for years and he felt as though he was carrying the revolution in molecular medicine on his shoulders. Anderson had been up all night finishing preparations on the five plastic bags of IV fluids the patient would receive, and obsessively writing down everything that happened.

As he silently observed the bedside drama, Anderson was afraid to breathe.

"The patient seemed serene," he recalls. "Hopeful, unafraid. But I was scared to death, of course. My worst fear was that the impossible would happen-that after everything all of us had been through, he would suffer a heart attack and die, right then and there."

One minute passed . . . "He`s OK."

Three minutes passed..."Absolutely uneventful," noted Anderson.

Five minutes . . . "Perfectly normal."

The participants relaxed a little.

After 45 minutes, the doctors moved on to other patients in the intensive care unit, their faces professionally masking feelings of overwhelming relief. "So far, so good," Anderson remembers thinking, emphasizing that the first experiment represents merely "a toe in the water; a foot in the door."

While important to the development of gene therapy, the experiment did not actually alter the patient`s genetic makeup and is a far cry from the classic goal of gene therapists: Permanently curing victims of inherited diseases by introducing healthy genes into their cells, or modifying genes already in place, or removing faulty genes and replacing them with good ones.

But the apparently safe gene transfer in the cancer experiment quickly led gene therapists to the next step: Two weeks ago, Anderson and his colleagues became the first scientists in history to seek permission to try genetic engineering in humans.