The aim of this project was to isolate a functional BoLA class I gene, to transfect this into L cells and to investigate the possibility of a second BoLa class I locus. Attempts to isolate a functional BoLA class I gene from a cosmid library were unsuccessful, but clones encoding complete BoLA genes were successfully identified from a bacteriophage library. This library was made from animal 10769 which has BoLA type w10/w11 and the genes were identified with a class I cDNA probe, pBoLA-1. These clones were transfected into mouse L cells to look for expression. One of the clones, 19.1, expressed class I molecules when analysed by indirect immunofluorescence on the FACScan and by fluorescence microscopy. The Northern blot analysis confirmed class I transcription products when probed with pBoLA-1. Clone 19.1 was identified as encoding a w11 gene by a microlymphocytotoxicity test. Also in a T cell cytotoxicity assay, Ltk 19.1 cells were killed by alloreactive anti w11 cytotoxic T cell clones but not by anti w10 clones. Nucleotide sequencing of gene encoded in 19.1 demonstrated homology between this and BoLA cDNA clones and HLA. Therefore a functional BoLA class I gene with a BoLA type w11 was isolated and is a stepping stone to many other investigations.