Nan Davis, a 22-year-old paraplegic, took five slow steps yesterday. It was the first time a paralyzed human being has walked under the control of an electronic computer firing electric commands to her helpless legs.

In a laboratory at Wright State University in Dayton, Ohio, Davis -- paralyzed from the waist down in an auto accident on her high school graduation night -- took the steps, smiled and said:

"It was fantastic. I feel like a pioneer. This is history, the first time it's ever been done."

The feat was performed Wednesday night, then repeated yesterday at a news conference in the Wright State biomedical engineering laboratories headed by Dr. Jerrold Petrofsky.

It was not yet the fully independent walking Petrofsky hopes to achieve for thousands of paraplegics. Davis was linked by wires to a small desktop computer. She gripped parallel bars to steady herself as she walked, and an overhead harness supported more than half her weight.

Nevertheless, one witness, Larry Kinneer, university communications head, said:

"She did walk. The electricity did move her muscles. She rose from a chair with the aid of the computer signals. She steadied herself on the rails. She moved one leg, then the other, and took steps, going eight or 10 feet. It was exciting and moving."

Petrofsky hopes to substitute a small, 6-by-10-inch computer, one carried over the shoulder like a handbag, for the desktop computer soon. He hopes to remove the overhead safety harness.

"Since no one has ever had a paraplegic or quadriplegic walk," he explained, "we don't know if their bones and muscles are in sufficiently good condition to safely support their body weight."

When Davis has had more practice and her bones and muscles have gained strength, she should be able to walk with no visible assistance, Petrofsky believes.

The help then, as yesterday, will come from the computer commands to 30 electrodes and sensors bearing tiny computers on chips, like those in electronic games and watches, linked to 10 muscle groups. The signals make muscles move. A feedback system controlled by the computer keeps the movements smooth and coordinated.

The electrodes were taped to Davis' waist and legs yesterday. Later, Petrofsky plans to implant them under the skin.

The potential for his development is tremendous. Some 3,000 Americans suffer paralyzing spine injuries in auto accidents alone every year.

Petrofsky warned that it will be 10 years at least before his system is ready for commercial development. He said the process can only help those whose peripheral motor nerves are uninjured.

Some researchers remain skeptical about early development of independent "computer walking."

Petrofsky said that this week's success "is just really another step forward and only the beginning of walking research."

The start, perhaps, was the 18th century experiments of Luigi Galvani, who used electric current to make animals' muscles contract. Petrofsky's work -- price tag so far, $400,000 -- began 13 years ago.

Last spring Davis pedaled a stationary bicycle while her muscles were stimulated by Petrofsky's computer. Then she rode a similar outdoor tricycle, building muscle strength and mass to restore the legs that had been useless since 1978.

"The knowledge of what is happening here will give people hope," Petrofsky said.