Heparan sulfate (HS) is an unbranched chain of repetitive disaccharides, which specifically binds ligands when attached to the cell surface or secreted extracellularly. HS chains contain sulfated domains, termed the HS fine structure, which give HS specific binding affinities for extracellular ligands. HS 2-O-sulfotransferase (2-OST) catalyzes the transfer of sulfate groups to the 2-O position of uronic acid residues of HS. We report here the characterization and developmental expression patterns of 2-OST in several tissues/organs throughout early zebrafish development, including early cleavage stages, eyes, somites, brain, internal organ primordial, and pectoral fin. The 2-OST gene has spatially and temporally distinct expression, which is a surprise given the essential role of 2-OST in HS fine structure formation. Furthermore, although 2-OST and C5-epimerase are predicted to be interdependent for protein translocation from the endoplasmic reticulum to the Golgi, their expression is not coordinately regulated during zebrafish development. Developmental Dynamics 236:581–586, 2007. © 2006 Wiley-Liss, Inc.