Hodgkin's lymphoma can be divided with the help of morphologic and immunohistochemical techniques into classical and nodular lymphocyte predominant Hodgkin's lymphoma. By single cell analyses it could be established that the tumor cells of Hodgkin's lymphoma are clonal B-cells with germinal center origin. In rare cases (less than 5 %), the Hodgkin and Reed Sternberg cells represent clonal tumor cells that derive from T-cells. By gene expression analyses it can be shown that Hodgkin cell lines represent an entity independently of their B- or T-cell-origin. Hodgkin cell lines show similarities to EBV transformed B-cells and in vitro activated B-cells. The genes found with the help of gene expression analyses may have crucial importance in the pathogenesis and are potentially new diagnostic markers and therapeutic targets.