A 1367 bp promoter region of the trout MT -B gene has been sequenced and this sequence was submitted to EMBL with an accession number X-58281. The sequence contains eight metal responsive elements (MREs)-MREa to MREh, The newly found M REs have unique features in that they are clustered together within 30 bp and occur in different orientations. This sequence also contains direct and inverted repeats and has the potential to form a secondary structure, In addition, four potential octamer elements were identified, two of which are in the vicinity of the M REa and MREb ln two different orientations, and the other two are on the very distal part of the prometer. Two putative adenovirus E1A enhancer elements and a cycilc AMP responsive element, CREB, that has a substantial homology to that of the consensus sequences were also shown to be present. Furthermore, two CAAT boxes were identified, one of which occurs within the CREB sequences. The data presented here clearly demonstrated that the promoter region is more complex than previously assumed. The promoter contains quite a diverge number of responsive element. The presence of these elements strongly suggests that the gene is involved in signal transduction.