We show that if G is a
group of permutations on a set of n points and if |G∕G′| denotes the order of
its largest abelian quotient, then either |G∕G′| = 1 or there is a prime p
dividing |G∕G′| such that |G∕G′|≤ pn∕p. Equality holds if and only if G is a
p-group which is the direct product of its transitive constituents, with each
of those having order p, except when p = 2 in which case one must also
allow as transitive constituents the groups of order 4, the dihedral group of
order 8 and degree 4, and the extraspecial group of order 32 and degree
8.