A human CD2 minigene cassette has been used in the past to express several reporter genes in the T cell lineage of transgenic mice. However, in order to achieve appreciable levels of expression it has been necessary to integrate many copies of the transgene. In this report we describe an improved version of this cassette. The new cassette directs the expression of a reporter mouse CD8 alpha cDNA on all T cells of transgenic mice with an efficiency ten times higher than the previous cassette. The new cassette includes 5 kb 5' and 5.5 kb 3' flanking sequences containing, respectively, the promoter and locus control region (LCR) of the human CD2 gene. The LCR confers position independent, transgene copy number dependent expression of the genes linked to it in transgenic mice. The cassette also provides a transcription initiation site, the first intron of human CD2 gene and the two polyadenylation signals found in the 3' untranslated region of hCD2 gene.