Tony Vinciquerra, president and chief executive of Fox Networks Group, said parents already have the controls they need on cable and satellite to block channels or programs they deem inappropriate.

Parents with regular over-the-air TV can use the V-chip, technology that's built into televisions and works with an electronically coded rating system to identify programs that contain sex, violence or crude language.

Vinciquerra also said network executives are aware of parents' concerns. "We have debates every minute of every day about what goes on television," he said.

Vicky Rideout, a vice president at Kaiser, said the number of shows that included a message about the risks and responsibilities of sex is still very small, and has remained flat since 2002.

About 14 percent of the shows with sexual content also had discussions of contraception, waiting to have sex or other "safer sex" messages. While that figure is about the same as it was in the last study, it's up from 9 percent in 1998.

The Henry J. Kaiser Family Foundation is a philanthropic group that studies health care, including reproductive and AIDS-related issues. It is not affiliated with the Kaiser medical organization.

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On the Net: Kaiser Family Foundation: www.kff.org