Marek's disease (MD) virus (MDV) serotype 1 (MDV1) pp38, an antigen associated with MD-transformed cells, has been identified as an MDV1 serotype-specific antigen by analyses using specific monoclonal antibodies (MAbs). In the present study, we determined the region in the MDV serotype 2 (MDV2) genome that has homology with the MDV1 pp38 gene. As a result of sequence analysis, it was determined that an open reading frame (ORF) existed in this region. Furthermore, Northern blot analysis and reverse transcriptase polymerase chain reaction confirmed the existence of an RNA transcript related to the ORF in MDV2-infected cells. Computer analyses revealed that MDV1 pp38 could be divided into two parts; one part was highly homologous and the other part was not homologous with the peptides deduced from the ORF of MDV2, indicating that the epitope recognized by a MDV1 pp38-specific MAb is located in the latter part.