Using the upstream region of glycoprotein E gene of pseudorabies virus (PRV) as a model, a method based on reverse transcriptase-polymerase chain reaction (RT-PCR) for the determination of transcriptional start site was developed. The conventional primer extension method was used to determine the start site. Comparing the results obtained by these two methods, a good agreement on the location of start site was achieved. In addition, a computer program was used to predict the transcriptional start site, and the predicted site was found to be close to the two sites obtained by experiments. Based on the transcriptional start site data and on the general knowledge of the eukaryotic gene, the TATA box of gE gene was assigned at approximately 33 bp upstream to the start site.