In order to improve the immune status of girls in our medical clinic, we conducted a prospective sero-survey to identify susceptibles and developed a system for vaccinating non-immune girls. Over an 18-month period, 481 inner-city adolescents were screened. Susceptibility rate defined by a titer less than 1:8 was 12 per cent and did not differ significantly with regard to age or race. Nine months into the study period, the State of Wisconsin enacted a "no immunization-no school" law. The susceptibility rate dropped from 22 per cent prior to the enactment of the law, to 5 per cent after. Of the 60 girls identified as susceptible, 54 (90 per cent) kept their follow up appointments for vaccinations. Enforced state immunization laws appear to be effective in lowering rubella susceptibility.