This paper presents the sensitivity analysis of an epidemiological model, SEIR, describing the transmission of Hepatitis B Virus. The classical sensitivities, the system sensitivity and the sensitivity norms of the model have been found. The sensitivities show that the susceptible individuals are majorly affected by the birth rate, contact rate, the rate at which the exposed individuals become infected and the fraction of the infected individuals in the population. System sensitivity describes the sensitivity of the whole model output with respect to all the parameters. The results of the classical sensitivities of the parameters are in agreement with the results given by the system sensitivities. The contact rate, β has the largest sensitivity norm and the exposed infected fraction of the population, t_1 has the least sensitivity norm. The qualitative and the quantitative sensitivity studies of the SEIR model reaffirm each other.