The origin and clonality of the Hodgkin and Reed-Sternberg (HRS) cells in Hodgkin's disease (HD) has been much debated. Recently, single cell PCR techniques were established, allowing the study of HRS cells at the single cell level. HRS cells were analysed for Ig gene rearrangements to reveal a potential origin from B lineage cells. Whereas one study did not detect any V gene rearrangements, such rearrangements were found in three other investigations. However, whereas our own group detected clonal V gene rearrangements in the HRS cells of 11 (10 classical and one lymphocyte predominant) out of 12 cases of HD and no rearrangements in the twelfth, Delabie et al. (Blood 1994; 84: 3291-8) described four cases of lymphocyte predominant HD with polyclonal V gene rearrangements and Hummel and colleagues detected monoclonal as well as polyclonal and "mixed' populations of HRS cells in cases of classical HD. Potential reasons for the differing results of those investigations are discussed.