Abstract: Interlocking concrete form modules (21) suitable for creating a concrete wall form is disclosed. The modules (21) have the general shape of a right rectangular parallelepiped with parallel side walls (23a, 23b) joined by integral webs (25a, 25b, 27a, 27b, 27c) that define a plurality of parallel elongate cavities (31). The edges of the side walls (23a, 23b) include tongues (33a, 33b) and grooves (35a, 35b) that allow the modules (21) to be interlocked to form a wall. The ends of the webs are undercut such that cavities between the modules are created when the modules are suitably interlocked. The between-the-module cavities lie orthogonal to the through-the-module cavities. The modules (21) are formed of an insulating material and left in place. Preferably, the tongues along one edge include notches aligned with the webs. In one embodiment, the modules (21) substantially entirely are formed of relatively dense (3-5 lb./ft..sup.3) expanded polystyrene (EPS).