Units in integral group rings

Abstract Let V = V ( Z [ G ]) denote the group of normalized units in the integral group ring Z [ G ] of the finite group G . In this paper, we show that G has a torsion-free normal complement N in V provided G is either the circle group of a nilpotent ring or that G has an abelian subgroup of index at most 2. The main difficulty is to prove in the latter case that N is torsion-free.