These results suggest it's not enough to tell people to use condoms - they also need to learn how to use them correctly, the authors note.
"The importance of condom use seems obvious, yet the results from this study demonstrate that it must be taught even to sexually experienced individuals and that the lack of correct use can be linked to infection," write Dr. Diane M. Grimley of the University of Alabama at Birmingham and her colleagues.
In the American Journal of Health Behavior, Grimley and her colleagues note that one in five adults in the U.S. currently has an incurable sexually transmitted disease (STD). Evidence suggests that using a condom can protect against STDs, but perhaps not if used incorrectly.
Grimley and her team interviewed 1124 people visiting an STD clinic about their use of condoms and if they made any mistakes while using a condom in the past 30 days.
More than half of the people interviewed during the study said they had not used a condom the last time they had sex.
Within the past month, more than 40 percent of both men and women said they had not squeezed air out of the tip of the condom before using it. More than 40 percent of men and more than 30 percent of women reported that a condom broke during intercourse in the last month.
About one third of men and women they had not held the base of a condom during withdrawal, and 24 percent of men and 30 percent of women did not leave a space at the tip of the condom. Many people also admitted they started having sex before using a condom.
Women were more likely to say they had not left space at the tip or removed air from the tip of a condom before using it, while men were more likely to say they put on a condom inside out or had a condom break.
More than 15 percent of study participants had either gonorrhea or chlamydia, some both. Men who said a condom had broken during the last 30 days were more than 90 percent more likely to have gonorrhea.
"The tendency to assume that consistent condom users are using condoms correctly seriously underestimates their risk of transmitting or contracting STDs or becoming pregnant unintentionally," Grimley and her team conclude.