We consider the set of ordered partitions of n into m parts acted upon by the cyclic permutation (12...m). The resulting family of orbits P(n, m) is shown to have cardinality p(n,m)=( 1 n∑ d mφ(d)( n d m d), where φ is Euler's φ-function. P(n, m) is shown to be set-isomorphic to the family of orbits C(n, m) of the set of all m-subsets of an n-set acted upon by the cyclic permutation (12...n). This isomorphism yields an efficient method for determining the complete weight enumerator of any code generated by a circulant matrix. © 1979.