Two cases of primary gastric Hodgkin's disease were examined morphologically and immunohistochemically. Immunogenetic studies were also made in one of the cases. Case 1 was diagnosed as nodular sclerosis and case 2 as mixed cellularity Hodgkin's disease. Large atypical mononuclear or multinucleated giant cells were immunohistochemically positive for BerH2, whereas they were negative for LCA, L26, DAKO CD3, MT1, UCHL-1, S100 protein, and MAC387. In case 1, large atypical cells examined immunohistochemically on frozen tissue specimens were positive for Ki-1 and negative for T- and B-cell markers. Southern blot hybridization studies performed on material from case 1 revealed germline configuration of immunoglobulin JH and T-cell-receptor beta-chain genes. To our knowledge, this is the first report in which primary gastric Hodgkin's disease has been studied immunogenetically. Although rare in incidence, the existence of Hodgkin's disease in the stomach must be noted.