Abstract: A pressure-sensitive lock for sliding windows and doors has rotatable eccentric cam means adapted to be mounted on the sash of a sliding window or door so as to engage the adjacent window frame when the cam means is rotated into the locking position. The lock also has a pressure block for mounting on the opposite side of the window adjacent the frame, such that when the cam means is placed in locking position against the frame, the sliding window is forced toward the opposite frame and the pressure block is thereby wedged against the frame to prevent the window from opening.