When I moved to San Francisco in 1997, Silicon Valley was in the midst of the dot-com frenzy. Coming from the far less-hip East Coast, I marveled at what seemed to be a Peninsula-wide psychosis.

Sure, the internet sizzled with possibilities, but the promises being made and the business plans proffered seemed more often nutty than not—an assessment that led more than one dotcom true believer to inform me that I just didn't get it, whatever it was.

Still, it was a heady moment for Web technology. Hundreds of startups participated in a culture-shifting, multibillion-dollar experiment to see what businesses would work online.

At the time, I likened it to World War I, when radical new technologies for killing people were tested by sending legions of 18-year-olds to the battlefields to step in front of them. Millions were killed while generals and politicians figured out what worked.

A brutal comparison, perhaps, but I do recall what seemed like legions of 28-year-olds being given millions by investors to set up everything from online designer-kibble stores to Web portals offering empowerment to the oppressed.

In Silicon Valley, much of this money seemed to go to some fabulous parties, foosball tables, and Razor scooters for every employee, and a good time was had by all.

The apparently sudden appearance of companies that want to test your DNA in order to help you plan appropriate recreational, health-care, and lifestyle choices; to determine ancestry, and to assess your predisposition for disease or criminal activity is a small, staid affair in comparison.

Investors are pouring in millions instead of billions, and there are virtually no parties. Even the toolmakers that make the sequencers and create the software to analyze genes have an aggregate market value of less than $1 billion.

The question is: Are we seeing the early stages of what will become a new flurry of companies rushing to the genetic front lines to see which business plans and technologies work for potential consumers of DNA-testing products?

Already, early leaders in one subset of the industry, the direct-to-consumer online genetics companies, are experimenting with various approaches to selling individuals information about what is hidden in their DNA.

The Google-backed 23andMe, down the peninsula from San Francisco, is mixing serious genetic markers associated with dreaded diseases with "recreational genetics"—finding out about "fun" traits such as caffeine resistance and a preference for mornings or evenings.

Iceland's deCODEme is offering a slightly more sober website featuring less fun and more information about gene markers for disease, many of which its parent company, deCODE, discovered.

Both 23andMe and deCODEme offer basic information on genealogical DNA-tracing one's genetic roots and links to ancestors.

The Bay Area-based Navigenics will open for business next month with a site devoted to the DNA of disease, with WebMD-like links to A-list medical institutions and a feature the other two websites do not have—phone access to live genetic counselors. Navigenics plans to charge about $2,500, compared with about $1,000 for 23andMe and deCODEme.

Other companies, such as DNA-Direct, in San Francisco, offer a test-by-test service, charging from the low hundreds to the low thousands of dollars for each test. These include Food and Drug Administration-approved diagnostic screening for, say, breast cancer. None of the markers offered by the other websites are F.D.A.-approved, and the sites take great pains to insist that their tests are informational-not medical diagnoses.

Many more DNA-testing companies exist on the Web, including those that specialize in just one area, such as genealogy, paternity, or nutrition. A few firms in this largely unregulated arena have attracted the attention of authorities in Europe and the U.S.

In 2006, a document issued jointly by the F.D.A., the Federal Trade Commission, and the Centers for Disease Control and Prevention warned consumers to be wary of some online nutrigenetics sites that offer dodgy tests that are used to sell expensive nutraceuticals-supplements and other dietary products with purported medical benefits.

A huge problem with these sites is that most genetic markers for diseases are incomplete and often not applicable to individuals. [For more information on this, see Welcome to the Future.]

I have a hard time imagining that these companies will reshape (perhaps warp?) my adopted city in the same way that the dotcoms of yore did. In the late 1990s, dotcoms covered the consumer landscape—from shoes and pornography to creating a "Second Life"—while genetics represents a much narrower slice of the pie.

Also, Web genetics companies will need to sequence a consumer's DNA only once, since genes stay largely the same throughout an individual's lifetime. There will be no Windows-style updates to genomes, though the analytical tools and programs will improve, and DNA websites will think of ever-edgier and more innovative ways to tell people about their genes.

None of this is likely to create a consumer-driven information company the size of a Microsoft or a Google, generating tens of billions of dollars. However, billions will be made by companies that use genetic information to develop custom drugs and devices. That process is already beginning with Herceptin from Genentech. This anticancer medicine, with revenue last year of $1.3 billion in the U.S., is given only to patients who test positive for a mutation in the HER2 gene.

Dotcoms may be remembered as the epitome of 1990s irrational exuberance, though of course the Battle of the Somme-like slaughter of youth largely worked. Online sales of virtually everything have exceeded even the most exuberant forecasts of a decade ago. Pets.com may be gone, for example, but I can buy almost anything pet related from PETCO.com.

I doubt that the DNA website market will ever be as wild or cool as the '90s dotcoms. Indeed, the very first thing that young genetics entrepreneurs-young meaning thirtysomething or even fortysomething-do to start DNA-testing services is recruit an award-winning Ph.D. geneticist or two along with a couple of famous physicians to legitimize their efforts.

This is another barrier to entry. Three guys fresh out of grad school with a harebrained idea aren't going to be taken seriously by investors or customers without connecting up with the establishment, something dotcomers mostly didn't have to worry about.

Personally, as I explore my own genome for a book due out this fall, I'm finding myself mostly confused by the information available. (More on this later.) Even early adopters I have talked to agree that, like the '90s dotcoms, much of the information isn't ready for prime time.

But it will be.

Genetics testing today is about where the internet was in 1986. Few people have even heard of the technology, but as Bob Dylan once sang, "There was music in the cafés at night/ And revolution in the air."