We investigated the effects of the concentration of disaccharides (trehalose, maltose, and sucrose) and the extrusion speed on the mean size of the unilamella vesicles (ULVs) by using the photon correlation spectroscopy (PCS). We found that the mean diameters of ULVs prepared in the solution with the same disaccharide concentration and the same extrusion speed were quite different. In the case of trehalose, the mean diameter of ULVs decreased as the disaccharide concentration decreased and the extrusion speed increased. Based on those findings, we could fabricate the uniform sized ULVs in different disaccharide solutions with the same concentration by controlling the extrusion speed. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.