We investigated how preschoolers use their understanding of the actions available to a speaker to resolve referential ambiguity. In this study, 58 3- and 4-year-olds were presented with arrays of eight objects in a toy house and were instructed to retrieve various objects from the display. The trials varied in terms of whether the speaker's hands were empty or full when she requested an object as well as whether the request was ambiguous (i.e., more than one potential referent) or unambiguous (i.e., only one potential referent). Results demonstrated that both 3- and 4-year-olds were sensitive to speaker action constraints and used this information to guide on-line processing (as indexed by eye gaze measures) and to make explicit referential decisions. (Contains 3 figures.)