A clone containing the gene ifngr2 for the second chain (IFN-gamma R2) of the mouse interferon gamma receptor complex was isolated from a cosmid library made of 129/Sv mouse genomic DNA. Sequence analysis revealed that the second chain is encoded by 7 exons. The complete gene spans about 17 kb of the genomic DNA. In the 5'-flanking region several transcription initiation sites between 27 and 136 nucleotides upstream from the translation initiation codon were mapped. This region has a high GC content, but no TATA or CAAT box. Potential binding sites were found for transcription factors Sp1, AP-2, NF1, EGR and NF kappa B. Promoter activity was assayed with a series of constructs with firefly luciferase as a reporter gene, under the control of the promoter fragments of various lengths. This region showed promoter activity in transiently transfected Chinese hamster ovary cells.