They were calls any ad sales person would be delighted to receive, and for John Morrison there had to be a sense of vindication.

For years, America's alternative newspapers relied on advertisers who couldn't afford to go into the dailies, such as local restaurants and clubs, and those whose ads were rejected, such as escort services. National advertisers were few, beyond beer and tobacco.

Then a funny thing happened. It began several years ago, and the pace has been picking up steadily with the troubles besetting so many major-city dailies.

Then came the spring round of newspaper circulation figures from the Audit Bureau of Circulations, and they were down again, disastrously for some papers. The San Francisco Chronicle was down 15.6 percent from a year earlier.

"We got some immediate reaction," recalls Morrison, who is sales director at the Alternative Weekly Network, which handles national advertising for 110 alt weeklies in the U.S. and Canada. "We immediately got calls from some advertisers that have traditionally advertised in newspapers like the Chronicle to do an analysis comparing those newspapers with our papers."

Increasingly, alt weeklies are seeming a lot more attractive to advertisers who would have shunned them five years ago, and the reasons are many. Certainly tops on the list is the accelerating circulation declines of so many dailies. Another is the circulation-cooking scandals of several years ago, which served to undermine the longstanding confidence many national advertiser had in ABC statements.

But perhaps the biggest selling point for the alt weeklies is their young readership, a readership so many advertisers want to reach and that dailies deliver fewer and fewer of as their readerships continue to age.

Morrison and others in the field say that national advertisers over recent year have become more comfortable with the idea of alternative weeklies.

"Over the course of the past several years, we've seen more diversification of our revenue, as opposed to five or 10 years ago, when it was mostly alcohol, tobacco and music," he says, and he says the leading growth categories include financial services, automotive, telecoms, packaged goods, broadcast and internet.

"We're starting to share a lot of the same accounts," he says, referring to the dailies. "It's a clear recognition on the part of advertisers that local print media is still a great advertising vehicle, but daily newspapers are only reaching a segment of the market. And we're reaching another segment, and what from their point of view may be a more desirable segment."

Alternative newspapers range from the nearly 250,000-circulation Village Voice to the 7,000-circ Texas Observer. Those in small and mid-size markets still rely on local ads for almost all their revenues, and even in larger markets local accounts still account for 80 to 90 percent of ad revenue, says Richard Karpel, president of the Association of Alternative Newsweeklies, a trade group.

But the alternative papers still have a hard sell in one critical area: their free circulation, and it is their greatest vulnerability in the eyes of industry analysts and competitors. They contend alt weekly circulation claims are not reliable, even though most are in fact audited at some level, either by ABC or Verified Audit, according to AAN.

"Their distribution is whatever they want it to be," says analyst John Morton. "The only newspapers that are measured are the paid dailies."

If dailies have had their circulation scandal, the circ figures for the alternatives are even more suspect, says Bob Shamberg, president of Newspaper Services of America, a major ad buying firm that places client ad dollars in both dailies and alternatives.

Jason Klein, CEO of Newspaper National Network, which reps dailies, agrees.

"There's very few real-time metrics on readership or circulation. Many major advertisers want to be in quality paid-circulation papers, and free distribution delivered from kiosks or boxes doesn't cut it. So there's a large segment of advertisers who just rule out free distribution weeklies."

Klein says alternatives' best argument is with advertisers that are looking to recast their images as younger skewing or are seeking aspirational readerships and are willing to accept the absence of solid circ data.

The AAN reports that 72 percent of alternative weekly readers are 18-49, a demographic that newspapers are aging out of.

"Alternative papers like the Boston Phoenix or the San Francisco Bay Guardian are as important for what they aren't as for what they are. Alternatives inhabit a different reader universe from dailies," Boston Phoenix editor Peter Kadzis says. According to Kadzis, the alt weekly identity helps insulate the papers from the effects of free dailies like the Metro and the Examiner chains.

But Morton warns that alternative weeklies are likely to suffer just as much as dailies from the shift toward the internet. Karpel says some major weeklies already have been impacted by the proliferation of internet classified sites like Craigslist and are responding online.

"About 50 alt-weeklies have responded by building their own free classifieds sites. I expect the rest to do the same within the next couple of years," Karpel says. "Many alt-weeklies have very active web sites with large readerships. However, none have been able to turn their web site into a substantial source of revenue yet."