Most translocations that occur in Burkitt's lymphoma involve movement of part of chromosome 8, containing the c-myc gene, from its normal position to the immunoglobulin heavy-chain locus on chromosome 14. The genes are often joined at their 5' ends in opposite transcriptional directions. However, a significant minority of Burkitt translocations involve the light-chain loci on chromosome 2 (kappa) or 22 (lambda). We have characterized one of these from a European-derived cell line (IARC-BL37) that carries an 8;22 translocation. Here the translocation has joined the 5' portion of the lambda light-chain locus to the 3' portion of the c-myc gene at a position about 7 kilobases from the normal c-myc promoters. The translocation is reciprocal and relatively conservative, involving the loss of only 21 base pairs from the site of recombination. This translocation allows us to orient the lambda genes with respect to the centromere of chromosome 22 and to predict the orientation of other translocations involving these chromosomal segments. The 3' translocation is accompanied by an increased level of c-myc transcripts, especially that derived from a normally under-used c-myc promoter.