Introduction: In adolescence, the risk of sexually transmissible diseases has increased, becoming necessary the implementation of prevention measures. Objective: to investigate the impact of the law of compulsory immunization on the immunization coverage against Hepatitis B in adolescents in the municipal district of Maringá-Pr. Method: This is a descriptive-exploratory study, of retrospective character, regarding the number of doses of the vaccine against Hepatitis B administered in the group of 10-19 years of age, from 2001 to 2008. Data was obtained from the records of the bank “Evaluation of the Immunization Program (EIP) – municipal module” and analyzed by the statistical tests: Analysis of Variance and Tukey. Results: Statistical difference was observed in the immunization coverage against Hepatitis B before and after the compulsory nature of the immunization certificate, and also among the months with greater interest for the vaccine in the period from October to February, which is school registration time. In the 15-19 year old group, an increase on the immunization coverage was observed from 2004 to 2006, with expressive drop in 2007 and 2008 when the two larger high education institutions ceased to ask for updated immunization records in the registration. Implications on Nursing: The results show the importance of health education for the adolescents and, in the mentioned scenario, the need for discussion of the results found together with the directors of high education institutions, in order to make them aware of the importance of including the immunization records among the documents demanded in the registration.