Let K[G] be the group algebra of a torsion group G over an infinite he
ld K, and let U = U(G) denote its group of units. A recent paper of A.
Giambruno, S. K. Sehgal, and A. Valenti proved that if U satisfies a
group identity, then K[G] satisfies a polynomial identity, thereby con
firming a conjecture of Brian Hartley. Here we add a footnote to their
result by showing that the commutator subgroup G' of G must have boun
ded period. Indeed, this additional fact enables us to obtain necessar
y and sufficient conditions for U(G) to satisfy an identity.