Abstract: A window assembly for a vehicle cab having first and second frames and a window horizontally divided into upper and lower sections. The upper section of the window is pivotally mounted to the top rail of the second frame which is totally surrounded by the first frame. The lower window section is hinged to the bottom of the upper window section and has a guide member on its bottom edge which mates with side guide rails formed in the second frame. The window is opened and closed by hydraulic cylinders which positively position and retain the window in a desired position regardless of the vibration or rocking motion experienced by the vehicle as it traverses over uneven terrain. Furthermore, the entire second frame can be opened by pivoting it about the upper edge of the first frame. In so doing, an alternative escape route is provided for leaving the confines of the cab.