Solute entrapment in vesicles is important fur drug delivery and gene transfer applications. Past studies have indicated that the extent of entrapment is influenced by the salt present during the process of freeze and thaw. In this report we show that even relatively low salt concentrations lead to a significant decrease in the entrapment yields, and we demonstrate that this decrease is the consequence of a morphological change of the vesicle suspension observed by cryo-transmission electron microscopy. Furthermore, monovalent salts present during the encapsulation process result in the formation of a species of lipid-rich structures, whereas most vesicles remain unaffected. In addition, we compare our experimental entrapment yields with theoretical values obtained under the assumption that the solute is uniformly dispersed inside and outside the vesicles and show that there is a relatively good agreement between experimental and theoretical values.