investigated.Thepropertiesoftheinsitugellingsystemwereestimatedbyrheologicalmeasurement.WhenPEG()concentrationwasvariedfromtowhileMC(SM)andSCconcentrationswerekeptconstantat.and.,respectively,thereversiblesol–geltransitiontemperatureloweredfrom_Cto_CwithincreasingPEGconcentration.However,theextentofloweringintemperaturewasnotinfluencedbythemolecularweightofPEG.Thereversiblesol–geltransitiontemperatureshiftedtowardsthelowertemperaturewithincreasingMCconcentration,andtowardsthehighertemperaturewithdecreasingpH.Comparisonofrheologicalpropertiesbetweenthepresentthermo-settinginsitugellingsolutionandaconventionalone,suchasgellangumsolutionorPoloxamersolution,revealedthatthepresentsolutionradicallydifferedfromtheconventionalsolutionsintheincipientgellingmechanism.Thesefindingssuggestthattheternarysysteminthisstudywouldbeusefulasadrugdeliverysystemforinstillationofdrugsintotheeye.KeywordsThermo-settinggelSol–geltransitiontemperatureRheologyMethylcellulose–polyethyleneglycol–citricac