Objective. The objective of this study was to evaluate the effect of an intervention with advance provision of emergency contraceptive pills (ECP), condoms, and extended information to a targeted group of teenage girls, compared with a control group, 12 months after intervention. Material and methods. A randomized controlled trial among 420 girls, 15-19 years old, requesting emergency contraception at a youth clinic in Sweden was carried out. Data were collected by a questionnaire at the initial visit and structured telephone interviews 12 months after enrolment. Differences between the intervention group and the control group regarding ECP use, time interval from unprotected intercourse to ECP intake, contraceptive use, and sexual risk-taking were analysed. Results. One year after the intervention 62% of the girls could be reached for follow-up. The girls in the intervention group reported a shorter time interval (mean 15.3 hours) from unprotected intercourse to ECP intake compared to the control group (mean 25.8 hours) (p = 0.019), without any evidence of decreased use of contraceptives or increased sexual risk-taking. Conclusion. Even up to 12 months following the intervention, advance provision of ECP at one single occasion, to a specific target group of adolescent girls, shortens the time interval from unprotected intercourse to pill intake, without jeopardizing contraceptive use or increasing sexual risk-taking. Considering the clinical relevance of these results, we suggest that advance provision of ECP could be implemented as a routine preventive measure for this target group.