To investigate the ability of cadmium to affect gene transcription in fish, the messenger RNA (mRNA) differential display technique was used to analyze gene expression in the Antarctic icefish Chionodraco hamatus exposed to sublethal doses of cadmium salt. Seven DNA complementary to RNA (cDNA) bands whose steady-state levels of expression significantly changed in response to cadmium exposure were identified. The results obtained show that two groups of genes are affected by cadmium in icefish liver. The first group comprises genes that are up-regulated by the metal: in particular, a gene encoding the heat-shock protein HSP70 and another encoding a protein homologous to GP49 of Sparus aurata egg envelope. The other group comprises genes down-regulated by cadmium. These are the transferrin gene and a gene encoding a protein presenting homology to mouse T2K, a kinase having a role in the prevention of apoptosis. Three cDNAs had no homology to known gene sequences, thus suggesting that may either encode not yet identified proteins, or correspond to untranslated regions of mRNA molecules.