Southern blot analysis of Hodgkin's disease (HD), although often compromised by the small number of abnormal cells present in the tissue, have tended to favor a B-cell derivation of the Hodgkin's and Reed-Sternberg (HRS) cells in cases of nodular sclerosis (NS) and mixed cellularity (MC) Hodgkin's disease. Eighteen frozen and 29 paraffin-embedded sections of lymph node specimens from 29 patients with pretreatment HD (22 NSHD and 7 MCHD) were studied by molecular analysis and immunohistochemistry to determine the phenotype of HRS cells. All cases were reviewed and showed typical morphology and CD45-, CD30+, CD15+, BLA.36+ HRS cells. In 11 of 29 (38%) cases, HRS cells were reactive with at least one B-cell marker (CD20, CD79a, MB2), 7 of 29 (24%) cases showed reactivity with the T-cell marker CD3, and 11 of 29 (38%) cases displayed a "null" phenotype. By using a polymerase chain reaction (PCR) and consensus primers for the V and J regions of the immunoglobulin heavy chain (IgH) gene, the authors were able to detect B-cell clonality in 9 of 18 (50%) frozen samples of HD analyzed. IgH gene rearrangement was present in 8 of 15 (53%) NSHD and in 1 of 3 (33%) MCHD. In five of nine (56%) of these cases, HRS cells were reactive with at least one B-cell marker, whereas one case expressed the T-cell marker CD3. The other three cases with IgH gene rearrangement showed a "null" immunophenotype. IgH gene analysis was negative in all remaining CD3+ cases and in two other cases that expressed B-cell markers by immunohistology. Southern blotting failed to detect rearrangement of the T-cell receptor beta-chain gene and immunoglobulin heavy and light genes in any of these cases. The results show that PCR represents a specific and sensitive technique for the detection of IgH gene rearrangements in cases of Hodgkin's disease. The results also suggest a lymphoid B-cell derivation of HRS cells in a high proportion of the cases.