Will There Be Blood? A flailing stem-cell company says it's invented synthetic blood. If so, it will mean a victory for stem cells.

Will bloodmobiles soon be a thing of the past, like vacuum-tube televisions and glass milk bottles delivered daily?

More important: Will the use of embryonic stem cells, which became a heated issue during the 2004 presidential election, finally produce a breakout product? One that will squelch the controversy for all but a few die-hards who still prefer their milk in glass bottles?

Researchers at Advanced Cell Technology in Worcester, Massachusetts, announced the breakthrough a few days ago. Working with scientists from the Mayo Clinic in Rochester, Minnesota, and the University of Chicago, A.C.T.'s team says it has developed a method for making potentially unlimited and scalable supplies of synthetic blood from embryonic stem cells.

The findings are published in Blood, a scientific journal. A.C.T.'s chief scientific officer Robert Lanza led the team.

If the claim holds up to scrutiny, it would be a huge boon for humankind, which until now has had to collectively open its veins to provide tons of this basic stuff of life for people who need extra blood because of injuries, surgeries, or disease.

The discovery also would remove the danger of blood being tainted by pathogens that cause hepatitis, H.I.V., and Creutzfeldt-Jakob disease, among other viruses and bacteria.

But will this promise become reality?

Advanced Cell Technology has made incredible claims before. Under recently departed C.E.O. Michael West-whom some critics compared with the circus promoter P.T. Barnum-the company routinely asserted that stem-cell therapies were likely to reverse the aging process and grow replacement body parts, while most scientists were talking a more cautious line.

The company was the first to clone an endangered species, an Asian bovine called a gaur, which died soon after-possibly from causes unrelated to the cloning. A.C.T. also claimed it had cloned the first human embryo, attracting worldwide attention, though the embryos grew to only a few cells in size.

Some blame the company's over-enthusiasm for playing into the hands of stem-cell opponents in the Bush Administration and elsewhere who were bent on squelching this new therapy. President Bush severely restricted federal funding for stem-cell research in 2001-restrictions that remain today, and are likely to until the next administration takes office.

Under Lanza, the company may not have fulfilled all of the promises made by West, but it has produced a string of solid discoveries and observations-though none have proved to be commercially viable. Most recently, Lanza's team has also induced stem cells to grow into retinal cells in eyes.

Creating synthetic blood has proved difficult; decades of efforts have so far been in vain. Several potential products are being tested in human clinical trials, most of them focusing on the critical function that blood plays in transporting oxygen. Other products, however, have been abandoned when they either didn't work, or proved to have dangerous or deadly side effects.

Blood created by stem cells is very similar to the real thing, and may avoid the pitfalls with other, more artificial techniques. If further tests confirm A.C.T.'s discovery-and, critically, show that the process is scalable and affordable-stem-cell blood may make the company more attractive to investors as it desperately seeks cash to carry on.

In July, a filing with the Securities and Exchange Commission revealed that A.C.T. had $17 million in current liabilities, but only $1 million in cash and other current assets, the Boston Globe reported. A.C.T.'s stock has been trading at 6 cents per share, down from $8 per share three years ago.

It's hard to know what the new techniques will cost once scaled up, or what revenues the discovery will bring in; Lanza says that he expects the company to know within two years if the processes will work.

Independent scientists are hopeful that the discovery will pan out. "The problem with relying on donated blood is that there are always shortages," Professor Alex Medvinsky, a blood stem-cell expert at the University of Edinburgh, told the Times of London. "The ability to generate red blood cells in very large numbers would be a very big thing."