Core/shell type acrylic-polyurethane hybrid microemulsions in which polyurethaneas the shell and acrylic polymer as the core were prepared successfully. Different cross-link-ing structures between core and shell can be formed by introducing hydroethyl acrylate andadipoyl dihydrazine at the ends of the polyurethane chains. The photon correlation spec-troscopy studies revealed that the mean particle size of the emulsions were smaller than 200nm. The particle morphology results revealed the core/shell structure of the uncross-linkingtype microemulsions and interpenetrating networks of the cross-linking type microemulsions.