Chromosomal translocations involving band 3q27 are recently described common specific cytogenetic abnormalities in B-cell neoplasms, and the BCL-6 gene, identified on 3q27, was shown to be disrupted and over-expressed in lymphoma cells having these chromosomal translocations. In the present study we found rearrangements within the BCL-6 gene in seven out of 35 cases with B-cell non-Hodgkin's lymphoma (NHL). Further analysis revealed that three of these patients with BCL-6 abnormality had multiple rearranged bands hybridized with probes from a single restriction fragment within the major translocation cluster (MTC), suggesting that independent DNA rearrangements would occur on both alleles. Additionally, Southern blot analysis indicated that three patients carry deletions encompassing the area containing the first exon of the BCL-6 gene. Our results suggest that biallelic DNA rearrangements and deletions would occasionally occur in NHL patients with BCL-6 abnormality.