Heavy metal ions are effective inducers of metallothionein gene transcription. The metal response is dependent on short DNA motifs, so‐called MREs (metal responsive elements) that occur in multiple copies in the promoter region of these genes. We have analysed an MRE of the mouse metallothionein‐I gene (MREd) and we demonstrate that this can function over long distances as a bona fide metal ion‐inducible enhancer. The transcription factor Sp1 and a zinc‐inducible factor, designated MTF‐1, bind to the MREd enhancer in vitro. The combined use of MREd mutants in a transient assay in HeLa cells and a competition band shift assay show that the zinc‐inducible formation of the MTF‐1/DNA complex in vitro correlates with zinc‐inducible transcription in vivo. A chemical methylation interference assay revealed remarkably similar but non‐identical guanine interference patterns for the MTF‐1 and Sp1 complexes, which may mean that MTF‐1 is related to the Sp1 factor.