The companies - NeoTactix Corp., Graystone Park Enterprises Inc., and Younger America Inc. - were among many touted in online videos posted on YouTube by a company called QualityStocks.net, the agency said.

The companies are small, "microcap" stocks that trade over-the-counter, rather than on a major exchange.

The SEC's chief of Internet enforcement John Stark said the suspension is the first enforcement action taken by the commission involving stocks promoted through online videos. It launched a campaign to stop stock spam last March.

The SEC said the three have "inadequately disclosed" their assets and financial conditions and are still under investigation. Trading suspensions can sometimes be followed by securities fraud charges.

Phone calls to NeoTactix Corp. and Younger America Inc. weren't immediately returned. Graystone Park Enterprises couldn't be reached for comment.

QualityStocks.net's promotion of the companies is part of the SEC's investigation. QualityStocks.net promotes newsletters on its Web site promising "Stock picks that GAIN 50 percent in a day."

Michael McCarthy, managing director of QualityStocks, said he was unaware of an SEC investigation and that QualityStocks doesn't have a financial relationship with any of the three companies.

The SEC said its anti-spam effort has cut complaints by 68 percent.