Abstract: A security device for windows comprising a first tube member pivotally secured at its lower end to the upper end of the lower window unit and having a second tube member slidably received on the upper end thereof. The upper end of the second tube member is pivotally secured to the window frame or to the upper end of the upper window unit. The first tube member has a plurality of spaced-apart openings formed therein which are adapted to receive a bolt extending therethrough. The window units may be moved relative to the window until the bolt engages the lower end of the second tube member to prevent further movement.