Objectives. We describe intervention effects on parent limits on novice teenage driving. Methods. We recruited parents and their 16-year-old children (n = 469) with learner's permits and randomized them from August 2000 to March 2003. Intervention families received persuasive newsletters related to high-risk teenage driving and a parent-teenager driving agreement; comparison families received standard information on driver safety. We conducted interviews when the adolescents obtained a learner's permit, upon licensure, and at 3, 6, and 12 months postlicensure. Results. Intervention parents and teenagers reported stricter limits on teen driving compared with the comparison group at 12 months, with direct effects through 3 months and indirect effects through 12 months postlicensure. Conclusions. A simple behavioral intervention was efficacious in increasing parental restriction of high-risk teen driving conditions among newly licensed drivers.