1046 base-pairs (bp) of genomic DNA spanning the first exon of the human alpha/beta-interferon (IFN)-inducible gene 6-16 have been analysed for their role in induction. The whole gene or 5'-flanking deletion derivatives of it were assayed for inducibility in populations of stably transfected mouse cells. 5'-Flanking DNA fragments were assayed for their ability to confer inducibility on a reporter gene in stably and transiently transfected mouse and human cells. The data suggest that a 39 bp sequence is sufficient to confer transcriptional inducibility and can account in large part for the response of 6-16. Two copies of this sequence, one of which contains a dinucleotide insert, are located in tandem 88 bp upstream of the 6-16 transcriptional initiation site. For at least one of the repeat units the 5' limit of a subregion required for induction lies in the sequence GGGAAAAT. The motif GGAAA occurs in several well characterized enhancers. Furthermore, one residue 3' of the GGAAA there is a second motif, TGAAACT, which is conserved in the regulatory regions of other IFN-induced genes. In gel retardation assays the oligonucleotide GGGAAAATGAAACT competes with the repeat element for binding to IFN-modulated protein(s) but a mutated oligonucleotide, GGGAAAATGACACT does not. These results identify an alpha/beta IFN response element partially homologous to those described previously for the genes of the MHC complexes.