The input to the {\em Graph Clustering Problem}\/
consists of a sequence of integers $m_1,...,m_t$
and a sequence of $\sum_{i=1}^{t}m_i$ graphs.
The question is whether the equivalence classes,
under the graph isomorphism relation,
of the input graphs have sizes which match the input sequence of integers.
In this note we show that this problem has a (perfect) zero-knowledge
interactive proof system.

This result improves over ECCC TR96-054,
where a parametrized (by the sequence of integers)
version of the problem was studied.