The region on chromosome 14q32.1 is frequently involved in chromosomal translocations and inversions with one of the T-cell receptor loci in human T-cell leukemias and lymphomas. The breakpoints of the different rearrangements segregate into two clusters: inversion on the centromeric side and simple balanced translocations on the telomeric side. If the target gene activated by these different types of chromosomal rearrangements is the same, the gene must reside between the two clusters of breakpoints in a region of approximately 160 kb. By screening of a placenta cDNA library using genomic probes derived from the vicinity of TCL1 locus, we have identified a gene coding for a 1.7-kb transcript that is expressed in leukemic cells carrying a t(14;14)(q11;q32) chromosome translocation. The cognate cDNA sequence reveals an open reading frame of 384 nucleotides encoding a Mr 15,000 protein with approximately 30% of homology with both p14TCL1 and p13MTCP1 oncoproteins. The genomic organization of the TML1 locus was characterized, with three exons located 15 kb from and tail-to-tail in relation to TCL1 locus. Because of its location and sequence similarity with TCL1 and MTCP1 oncoproteins, this gene, named TML1 (TCL1/MTCP1-like 1) is a candidate gene that is potentially involved in leukemogenesis.