The rheological properties of agarose solutions were examined under the effect of entanglement coupling between agarose chains. Agarose solutions were prepared by using an ionic liquid 1-butyl-3-methylimidazolium chloride as a solvent. The concentration of agarose was varied from 1.1 x 1012.1 x 102 kg m-3. The master curves of the angular frequency (omega) dependence of the storage modulus (G') and the loss modulus (G'') showed a rubbery region in the middle omega region and a flow region at low ? region, respectively. The molecular weight between entanglements (Me) for agarose was calculated from the plateau modulus. Moreover, Me for agarose melt was determined to be 2.3 x 103 from the concentration dependence curve of Me. By using well-known empirical relations in polymer rheology, information on molecular characteristics of sample agarose was derived. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012