Abstract: A lateral sliding sash comprises a sash frame having upper and lower frame members and two upright frame members; a first sash piece slidably mounted on the sash frame; a second sash piece; two sets of sliding members slidably mounted on the lower and upper frame members, respectively, the sliding members of each set being separated a predetermined distance and capable of being moved together; and two sets of linkarms pivotally connected to the sets of sliding members at their one ends, and to the lower and upper surfaces of the second sash piece at their other ends, respectively. The linkarms of each set are parallel to each other, so that the second sash piece can be pushed to engage in the sash frame and in alignment with the first sash piece, and can be pulled to disengage from the sash frame by the movements of the sets of linkarms and slid laterally with the sets of sliding members along the lower and upper frame members.