Background & Aim:  Hepatitis B virus vaccination, Ab titer of particular importance in health care workers is high. Due to the fact that the rate of immunization against the disease is not directly measurable, the presence of detectable levels of antibody in the serum of the vaccinated individual, the individual's immunity against disease is considered to be equivalent. The aim of this study was to evaluating the immunity against hepatitis B virus among Yasuj University of Medical Sciences students. Methods: In this cross - sectional study using purposive sampling 120 students input 2007-2010 were selected. After completing a questionnaire including demographic information and immunization records 5 ml of blood was taken. After separating serum using an ELISA kit specific antibody levels were measured against hepatitis B virus. The data collected was analyzed using descriptive statistics, chi-square test and analysis of variance. Results: In 74.16% of students the specific IgG Ab against the hepatitis B virus surface Ag were more than 20 IU/L, which is secure and in 19.16% of  them the Ab titer was below 10 IU/L which is non immune and  in 6.68% of students the Ab titer was between 10-20 IU/L that were borderline. Also in those who had received complete vaccination, immunization rates were     96.67 %. Conclusion: This study showed if vaccination against hepatitis B was complete, would be a high degree of immunity.