Abstract: The invention pertains to apparatus for forming elongated concrete structures, such as walls and the like, by slip forming. In particular, the invention is directed to the concept of slip forming walls of asymmetrical transverse cross section as required in the forming of highway barrier walls. The concrete slip form includes opposite sidewalls and open front and rear ends. At least one of the sidewalls is vertically adjustable wherein the sidewall configuration being formed thereby may have a height variance with respect to the opposite sidewall being formed. The form includes fixed wall portions associating with the adjustable wall portion and power means permit adjustment of the vertical adjustable wall. It is also within the scope of the invention to provide a form wherein both sidewalls are vertically adjustable, and the form includes means for introducing steel reinforcement into the formed wall, and periodically permitting accessory equipment to be embedded into the wall.