Washington ? Waiting to have sex is a nice idea, teenagers say, but they believe hardly anyone does it.

Many teens, particularly boys, feel pressure to have sex, and they say drugs and alcohol often lead to sex — often without condoms.

The teen survey by the Kaiser Family Foundation measured youth attitudes about sex and the risk of pregnancy and sexually transmitted diseases.

Teen pregnancy and birth rates have been falling for a decade — a trend that other surveys have attributed to a drop in sexual activity and an increased use of condoms and other forms of birth control.

Still, the Kaiser survey spotlights areas of concern: Four in 10 sexually active teenagers have taken a pregnancy test or had a partner who did so. A significant minority of young people — about one in six — say having sex without a condom occasionally is not a big deal. And one in five say they have had unprotected sex after drinking or using drugs.

Separately, the National Campaign to Prevent Teen Pregnancy released its own study Tuesday examining sex among younger teens. It found that about one in five teens report having sex before they turn 15 years old.

That report, a compilation of data from earlier surveys, also found that younger teen girls who are sexually experienced were more likely than older teens to say they wish they had waited to have sex.