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@@ Despite a large number of reports on mixed surfactant systems and formation of mixed micelles in aqueous and aqueous—organic solvents in the literature，there are fewer reports on the interfacial and other properties of the mixed systems under hard water conditions．We have investigated the micellar behaviour of mixed systems composed of an anionic surfactant like sodium dodecyl sulphate(SDS)or Linear Alkyl Benzene Sulfonate(LAB S)and a non—ionic surfactant TritonX-1 00 in mixed aqueous--organic solvent media in presence of water hardness ions from surface tension，conductometry，turbidity and light scattering measurements．The organic solvents chosen for the study include homologues of ethylene glycol(EG)，polyethylene glycol(PEG)and lower members of aliphatic alcohols．Presence of water hardness ions at low levels at least up to 50 ppm for LABS or 20 ppm for SDS appeared to promote the micellization of the anionic surfactants．But at higher ppm level，the hardness ions start manifesting its deleterious effects．The hardness tolerance of the mixed systems was found to be much superior to that of the pure systems．Presence of homologues of EG or PEG led to delaying the micelle formation while presence of the aliphatic alcohols tend to promote it．The effect is more pronounced with increase in the hydrophobicity of the added CO—solvent．The mixed systems have been analysed within the framework ofpseudo phases separation models and the interaction parameter，p，have been computed．The results showed that negative value of p initially decreased with water hardness up to about 50 ppm hardness followed by an increase at higher ppm．