The D14S7 locus defines the breakpoint on chromosome 14 of a t (8;14) (q24;q11) present in the T-cell line KE37-R in which DI4S7 sequences translocate 3' to the c-myc oncogene. It has been shown previously that DI4S7 rearranges specifically in some but not all T cell clones and in the present study we investigated the frequency and specificity of its rearrangements in human fresh lymphoma samples. DI4S7 rearrangements were extremely specific since they were detected in 3 out of 5 T-cell lymphoma samples positive for TCR beta and gamma but not in 17 miscellaneous non-T lymphomas, 4 non neoplastic lymphnodes as well as unstimulated and activated polyclonal T-cells. Most of the rearrangements were in the form of deletions that appear to involve large pieces of DNA since the segments detected by a V alpha probe were also deleted. Rearrangement of DI4S7 and V alpha regions were detected in lymphomas with a cortical thymocyte phenotype, demonstrating that they appear quite early in the differentiation of T cells.