The aim of the study was to test for relationships between state-level sex educational policies and sexually transmitted disease (STD) rates. We analysed US case reports of gonorrhoea and chlamydial infection for 2001-2005 against state policies for abstinence coverage in sexuality education, using the proportion of the population per state who identified as black (aged 15-24 years) as a covariate. We also tested for effects on 15-19 year olds versus 35-39 year olds and tuberculosis rates (the latter to ensure findings applied only to STD). States with no mandates for abstinence had the lowest mean rates of infection among the overall population and among adolescents. States with mandates emphasizing abstinence had the highest rates; states with mandates to cover (but not emphasize) abstinence fell in between. Rates in some states covering abstinence changed faster than in others, as reflected in sharper declines (gonorrhoea) or slower increases (chlamydial infection). These effects were not shown for tuberculosis or 35-39 year olds. Having no abstinence education policy has no apparent effect on STD rates for adolescents. For states with elevated rates, policies mandating coverage may be useful, although policies emphasizing abstinence show no benefit.