This review summarizes the occurrence, properties and role in mucin O-glycosylation pathways of the various members of glycoprotein sulphotransferase families. Although a number of sulphotransferases have been cloned that act on mucin-type substrates in vitro, it is still difficult to determine exactly which enzymes are responsible for mucin sulphation in vivo. Sulphotransferases play a critical role in determining the chemical, physical and biological properties of mucins. Several of these enzymes have been shown to differ in expression and activity in cancer and inflammation.