A case of syncytial variant of nodular sclerosing Hodgkin's disease in a 34-year-old woman is reported. Histologically, numerous Reed-Sternberg (RS) cells and their variants were seen in sheets. They were positive for CD30, CD15, CD25, and HLA-DR antigens. In addition, they expressed CD45 antigen and T-cell antigens (CD2, CD4). Molecular genetic analysis showed that this case had a germ line configuration for T-cell receptor (TCR) beta chain, TCR gamma chain, and immunoglobulin heavy chain genes. The percentage of the neoplastic cells in the specimen identified by CD30 positive cells was about 20% which was far above sensitivity of the molecular genetic analysis. Such analysis is reliable as to judgement of the results. Thus, these findings suggest that the RS cells and their variants in the present case are not derived from mature T cell in spite of their T-cell antigens expression.