Because of the rapid development of genital warts (GW) after infection, monitoring GW trends may provide early evidence of population-level human papillomavirus (HPV) vaccine effectiveness. Trends in GW diagnoses were assessed using public family planning administrative data. Between 2007 and 2010, among females younger than 21 years, these diagnoses decreased 35% from 0.94% to 0.61% (P(trend) < .001). Decreases were also observed among males younger than 21 years (19%); and among females and males ages 21-25 (10% and 11%, respectively). The diagnoses stabilized or increased among older age groups. HPV vaccine may be preventing GW among young people.