Let U(K(lambda)G) be the group of units of the infinite twisted group
algebra K(lambda)G over a field K. We describe the FC-centre Delta U o
f LI(K(lambda)G) and give a characterization of the groups G and field
s K for which LI(K(lambda)G) = Delta U. In the case of group algebras
we obtain the Cliff-Sehgal-Zassenhaus theorem.