As a first step toward developing a zebrafish model for investigating the role of sulfation in counteracting environ-mental estrogenic chemicals, we have embarked on the identification and characterization of cytosolic sulfotrans-ferases (STs) in zebrafish. By searching the zebrafish expressed sequence tag database, we have identified two cDNA clones encoding putative cytosolic STs. These two zebrafish ST cDNAs were isolated and subjected to nuc-leotide sequencing. Sequence data revealed that the two zebrafishSTs are highlyhomologous, being 82%identical in their amino acid sequences