To investigate the role of the BCL-2 gene in Japanese patients with B-cell non-Hodgkin's lymphoma, karyotypic analysis, DNA analysis and clinical characterization were studied. Ten of 73 patients showed t(14;18) and two patients had variant translocations [t(2;18) and t(18;22), respectively]. Of 42 patients examined at the molecular level, eight patients showed the BCL-2 gene rearrangement detected by mbr probe and two patients by 5'BCL-2 probe. Of the eight patients with the BCL-2 gene rearrangement by the mbr probe, t(14;18) was detected in six patients. A discrepancy in the relationship between the occurrence of t(14;18) and BCL-2 gene rearrangement was recognized. Two patients with obvious t(14;18) showed no rearrangement of the BCL-2 gene by mbr, mcr, nor 5' probe. Cytogenetic analysis is an indispensable tool for investigating lymphomogenesis. The two patients with the variant translocations, t(2;18) and t(18;22), showed breakpoints at the 5' site of the BCL-2 gene and both were histologically of the small lymphocytic type. No examples with the co-existence of both the BCL-2 and c-MYC gene rearrangements were found. The median survival time of the patients with the BCL-2 rearrangement and/or t(14;18) was longer than the patients without the BCL-2 gene rearrangement and translocation and also patients with the c-MYC gene rearrangement and/or translocation. Racial and geographical heterogeneities, variant translocations of t(14;18) and the clinical characteristics of B-cell non-Hodgkin's lymphoma with t(14;18) are discussed.