Abstract: This invention relates to a wall element for use in constructing walls, and a wall system constructed of two parallel rows of a plurality of the wall elements laid in courses in interconnecting relationship, the wall system being used as construction forms for retaining fluid concrete poured into the space therebetween, whereby the two walls remain as a permanent part of the completed wall system, and a method of constructing the described wall system from the wall elements and accessory parts. The invention includes a wall element for use in association with other similar wall elements in the construction of a wall. The wall element has a top, a bottom, two side and two end surfaces, and at least one longitudinal groove in the top or bottom surface thereof, and a matching longitudinal ridge in the opposite top or bottom surface thereof, and second and third horizontal longitudinally extending grooves on at least the top surface of the wall element, both being parallel to the first longitudinal groove.