BACKGROUND: In April 2007, Australia became the first country to introduce a national government-funded human papillomavirus (HPV) vaccination program. We evaluated the program's impact on genotype-specific HPV infection prevalence through a repeat survey of women attending clinical services. METHODS: HPV genoprevalence in women aged 18-24 years attending family planning clinics in the prevaccine period (2005-2007) was compared with prevalence among women of the same age group in the postvaccine period (2010-2011). The same recruitment and testing strategies were utilized for both sets of samples, and comparisons were adjusted for potentially confounding variables. RESULTS: The prevalence of vaccine HPV genotypes (6, 11, 16, and 18) was significantly lower in the postvaccine sample than in the prevaccine sample (6.7% vs 28.7%; P < .001), with lower prevalence observed in both vaccinated and unvaccinated women compared with the prevaccine population (5.0% [adjusted odds ratio, 0.11; 95% confidence interval, 0.06-0.21] and 15.8% [adjusted odds ratio, 0.42; 95% confidence interval, 0.19-0.93], respectively). A slightly lower prevalence of nonvaccine oncogenic HPV genotypes was also found in vaccinated women (30.8% vs 37.6%; adjusted odds ratio, 0.68; 95% confidence interval, 0.46-0.99). CONCLUSIONS: Four years after the commencement of the Australian HPV vaccination program, a substantial decrease in vaccine-targeted genotypes is evident and should, in time, translate into reductions in HPV-related lesions.