BERKELEY, CALIF., JUNE 22 -- Two groups of physicists reported today that they have developed materials showing tantalizing signs of being superconductors of electricity near room temperature.

Groups from the University of Houston and the University of California at Berkeley told an international conference here that they now have solid evidence that some materials lose all resistance to electricity at temperatures in the range of 65 degrees Fahrenheit. But an international conference here they said they had been unable to reproduce their results or fully comprehend how they achieved them.

High-temperature superconductors, which allow energy to flow without wasteful resistance, were discovered last year. In the past few months breakthroughs in research have accelerated so rapidly that achieving superconductivity at room temperature, a goal only recently considered years away, is considered imminent by many scientists. If room-temperature superconductors could be turned into wires and films, they would offer incalculable savings in energy.

Rumors have been circulating for weeks that several laboratories have reached the verge of room-temperature devices. In part because of potentially high stakes involved in the race, neither group today would describe its new material.

Although advancement has been rapid, scientists remain far from being able to translate discoveries into practical applications. This meeting, bringing together 500 scientists from around the world, was convened in an attempt to answer many questions about the new materials.

"We saw it go to about 300 degrees Kelvin," or 78 degrees Fahrenheit, said Paul C. W. Chu, the University of Houston physicist who is one of the field's leaders, in discussing his team's progress. "It retained its superconducting properties. But we still have problems with stability and reproducing it. We really believe that eventually we will reproduce it."

The Berkeley group, led by Alex Zettel and Marvin Cohen, also reported unstable superconductivity at 68 degrees Fahrenheit. Other groups are expected to report similar results Wednesday.

By unstable, the scientists mean that when the material was heated to higher temperatures it lost ability to act as a superconductor, possibly because the heat causes a reaction that breaks the chemical bonds needed to hold the atoms together.

The phenomenon of superconductivity has been known for years, but to achieve it, physicists until last year had to cool materials to almost 400 degrees below zero Fahrenheit. That kept most applications beyond reach.

To be considered a superconductor, a material must not only lose resistance to electrical flow but also be able to repel a magnetic field.

Chu said his material did both, but along only 1 percent of its total surface. In the past, he and others had seen evidence of loss of resistance but not the ability to repel the magnetic field. Chu reported today that at 225 degrees Kelvin, or 54 degrees below zero Fahrenheit, his lab was able to repel the magnetic field for almost a month of operation.

C.Y. Huang of Lockheed Research Laboratory in Palo Alto, Calif., who worked with Chu, said that he was now certain scientists will be able to achieve a stable room-temperature superconductor.

"We just have to figure out how this worked," he said. "And we are beginning to have some idea. It's not too early for optimism. But it's too early to talk."

Others at the meeting have voiced concern that, while the pace of discovery has been astonishing, scientists should reveal results with caution.

"There are other reasons why this phenomenon could occur," said Paul Grant, manager of the superconductivity project at International Business Machines Corp.'s Almaden, Calif., research facility. "In science, reproducibility is everything."

He and others at the conference agreed that reproducing results without understanding the mechanism has been difficult.

"We are almost randomly mixing with different elements in an attempt to find something that works right," he said.