Nevertheless, he expressed concern that the so-called v-chip technology that lets parents filter content cannot block advertisements, including spots for candy, fast food, sugary cereals and unhealthy snacks that youngsters routinely see. In 1996, Markey spearheaded efforts to include v-chips in television sets, but the technology has drawn scrutiny from critics who complain it is too complicated and not widely known.

"I urge the industry to look at ways to make the technological tools parents already possess more useful and to better advertise their availability," he added. Markey may ask the FCC to initiate a rulemaking on children's advertising.

Friday's hearing was announced after the Senate Commerce Committee scheduled a June 26 hearing on curbing television violence. Rockefeller originally planned to offer legislation shortly that would permit the FCC to regulate excessively graphic TV scenes. But a recent court decision overturning agency policy governing "fleeting" on-air profanity during live programming has prompted Rockefeller to rethink his bill.

Spokesman Steven Broderick said the West Virginia lawmaker may add language clarifying the FCC's authority to curb indecency if the agency doesn't appeal the ruling. The senator, who has delayed his measure by a few weeks, also plans to request additional hearings examining media programming and commercials.

During Friday's hearing, some witnesses and lawmakers blamed diabetes, obesity and cigarette use among youngsters partly on extensive TV viewing and regular exposure to junk-food ads and depictions of smoking. But Rep. Fred Upton of Michigan, the subcommittee's ranking Republican, emphasized that parental involvement is paramount.

"We have drifted away from personal responsibility,” he said, adding, "The master of the clicker must be the adult, not the child in the household."

Dan Glickman, chairman and chief executive officer of the Motion Picture Association of America, testified that film and television ratings already give parents considerable control over what they let their children watch. He noted that MPAA has added "stern" warnings to R-rated films and recently factored smoking scenes into ratings.

"Government edicts alone won't solve the problem," he said.

Kyle McSlarrow, president of the National Cable and Telecommunications Association, said his industry has done more than any other to offer family-friendly options. While cable's parental controls are not perfect, he considers them "pretty good" and pledged to work with lawmakers to make improvements.

Testifying on behalf of the National Association of Broadcasters, Jon Rand, general manager of a Fox television station in Spokane, Wash., warned that regulating TV advertising might have the chilling effect of diminishing the availability and quality of children's programming.