Translocation t(3;22)(q27;q11) has recently been recognized as a recurrent abnormality in non-Hodgkin's malignant lymphoma (NHL). A new gene, LAZ3, has been shown to be involved in NHL with 3q27 rearrangement. Two patients with B-cell NHL were studied by chromosome painting and Southern blot analysis. Fluorescence in situ hybridization to metaphase chromosomes was shown to be an easy way to detect the chromosomal abnormality even in metaphase cells with poorly defined chromosomes. The gene LAZ3 was rearranged in one patient in the 'major translocation cluster region'. The comigration of rearranged LAZ3 and of IGL bands suggests that the translocation resulted in the juxtaposition of the two genes. This juxtaposition makes possible a potential deregulation of the LAZ3 gene expression, as previously shown for the MYC and BCL2 genes in Burkitt and follicular lymphoma translocations.