Virginity pledges do deter some teens from having sex, according to a study by the RAND Corp. that surveyed teen virgins over three years to see whether they stayed that way.

Of 1,517 adolescents ages 12 to 17 in 2001 when the research began, teenagers who vowed to remain virgins until they were married were less likely to be sexually active than others who didn't make a pledge.

About one-quarter of the adolescents surveyed (23.8 percent) made a promise to wait until marriage to have sex; 34 percent had broken it by 2004, compared with 42 percent of those who didn't make the pledge and had sex during that time.

Those who pledged and those who didn't had similar responses in the telephone survey on questions about their parents' disapproval of sex, their self-esteem, their perceived peer approval of sex and their parental monitoring, among others.

Among those already inclined to delay sexual activity, the pledge may have served as extra protection, says RAND psychologist Steven Martino of Pittsburgh, the study's lead author.

"If it's your intention as a teen to not have sex, it's perhaps a good idea to make a pledge because you're more likely to delay sex if you do so and not more likely to engage in other sexual behaviors as a substitute," he says.

"But that's not to say virginity pledges should substitute for comprehensive sex education, because a majority of teens do have sex, and even among teens who take virginity pledges, many of them have sex," Martino says.

Valerie Huber, executive director of the National Abstinence Education Association, which supports abstinence-only sex education, disagrees.

EDUCATION STRESSED

"A lot of people would say a virginity pledge is an equivalent to an abstinence education program. It's certainly not," she says. "It's a single event with a personal commitment, but there's often not follow-up.

"We think abstinence education is a natural reinforcement of this personal decision they have made."

The new analysis, published online in the Journal of Adolescent Health in advance of print publication in September, is the latest attempt to determine whether virginity pledges are effective.

Some studies suggest they do help postpone first-time sex among teens, and other research suggests they don't. Also, there are questions about how truthful teens are when answering questions about sex.

"There is conflicting data on the worth" of pledges, Martino says.

He says his research took into account characteristics shared between those who made the pledge and those who didn't, so the major difference between them was taking the pledge.

Although virginity pledges appear to make a difference for some teens, Martino says, they probably don't do the same for adolescents overall.

Past research has found that 23 percent of teenage girls and 16 percent of boys have made a virginity pledge.