Objective: The aim of this study was to enhance the level of knowledge of the 4th year students of Istanbul Faculty of Medicine on Hepatitis B from the public health point of view by a training practice, and to measure their knowledge levels before and after the practice and compare these results. Materials and methods: This is an intervention study. In the 2nd term of the academic year 2003 - 2004 (in January 20, March 16, April 27, 2004), 95 students were given interview forms consisting of 30 items which were related to the ways of infection of Hepatitis B and the means of protection from the disease. At the beginning of the practice, students were asked whether they had been vaccinated before. After 20 minutes of interactive training, the same forms were applied again. The scores of the students were recorded before and after the practice and compared using the Wilcoxon Sign Test. Results: The median value of 95 students was 28 (min:25; max:30) before the practice; and median: 30 (min: 26; max: 30) after it. It was found that there were statistically significant increases in the knowledge levels of the students after the practice (z=7.3, p=0.0001). 87.4 % of the students had been vaccinated against Hepatitis B at least once. 4.8 % of the vaccinated students were vaccinated 2 times; 86.7 % 3 times; 7.2 % 4 times; and 1.2 % 5 times. Conclusion: In the field of preventive medicine, people should have sound knowledge about the ways of infection of and means of protection from Hepatitis B. Medical students in Turkey should be well informed of this subject and the vaccination rates should be increased as Turkey is a country having a medium level of endemic rate regarding this disease. Our study has shown that the level of knowledge of our students was high and their lack of knowledge concerning the subject was made up for thoroughly after the interactive training practice. Furthermore, students were also tested for HBsAg and HbsAc and reminded to get vaccinated.