The Saccharomyces cerevisiae genome contains nine open reading frames (ORFs)--YLR214w (FRE1), YKL220c (FRE2), YOR381w, YNR060w, YOR384w, YLL051c, YOL152w, YGL160w and YLR047c--which, based on amino acid sequence similarity, fall in the category of iron/copper reductase-related genes. FRE1 and FRE2 are the first identified and studied genes of this family. They both encode for plasma membrane ferric/cupric reductases and their expression is regulated by iron and copper availability, mediated by the transcription factors Aft1p and Mac1p, respectively. We have studied the expression of the seven ORFs of unknown function by monitoring mRNA accumulation under different growth conditions, namely, their response to iron and copper availability in the medium, as well as the involvement of transcription factors Aft1p and Mac1p in their expression. A compilation of these results, together with sequence comparison data, permits a first classification of these genes under three major groups: genes mainly regulated by iron availability, genes mainly regulated by copper availability and genes not regulated by either metal.