Alginate possesses many favorable properties required for biomaterials such as biocompatibility and gelation under gentle conditions.The critical behaviour of the sol-gel transition in aqueous alginate solutions induced by cations was affected by many factors

including the molecular weight and molecular structure sequence of alginate and the kind of cations.The critical exponents suggested two categories of the gelation as growth and crosslink according to molecular size in the solution just before the gelation.Alginate is widely used in tissue-engineered cartilages and drug controlled release.This review seeks to condense information in developing materials for these applications.