Phase diagrams of the ternary system water/poly(12-hydroxystearic acid)-poly(ethylene oxide)-poly(12-hydroxystearic acid) (PHS-PEO-PHS)/isopropyl myristate and the quaternary system water/PHS-PEO-PHS/1,2-alkanediol/isopropyl myristate were investigated at 25 degreesC. The alkanediols tested in this work are 1,2-hexanediol and 1,2-octanediol. The different phases formed have been examined by optical (phase contrast and polarizing) microscopy. The nature of the continuous media has been determined by conductivity. Particular attention was paid to the L-2 (water-in-oil micoremulsion). The amount of water solubilized in this region increases as the surfactant concentration increases. The minimum. content of polymeric surfactant and cosurfactant for maximum water solubilization is about 37%. The present investigation has also shown the relation between the oil polarity and the maximum water content that can be solubilized in microemulsions.