Among Antarctic notothenioids, appreciable amounts of hepatic metallothionein were found in red‐blooded species, whilst very little metallothionein, if any, was detected in icefish. In contrast, high levels of metallothionein mRNA were revealed in both fishes by Northern blot analysis of total RNA. Phylogenetic analyses carried out on the metallothionein sequences obtained by using reverse‐transcriptase polymerase chain reaction on eight notothenioid species revealed that notothenioid metallothioneins can be divided into two groups, metallothionein‐I and metallothionein‐II, indicating that they arose from at least one gene duplication event occurring in the ancestral lineage of the Notothenioidei. A strong induction of metallothionein gene expression and metallothionein accumulation could be obtained in icefish injected with cadmium salt. Apparently, the expression of the genes encoding MT‐I and MT‐II in icefish liver is differentially regulated by cadmium. The discrepancy between metallothionein mRNA levels and amounts of metallothionein protein observed in icefish was observed also in red‐blooded species. InNotothenia coriiceps,the profile of metallothionein mRNA accumulation, as well as that of the metallothionein levels, differs substantially in different tissues suggesting the presence of an organ‐specific regulation of metallothionein genes.