Palsberg and Zhao~\cite{PalsbergZhao00} presented an $O(n^2)$ time
algorithm for matching two recursive types. In this paper, we present
an $O(n \log n)$ algorithm for the same problem. Our algorithm works
by reducing the type matching problem to the well-understood problem
of finding a size-stable partition of a graph. Our result may help
improve systems, such as Polyspin and Mockingbird, that are designed
to facilitate interoperability of software components. We also discuss
possible applications of our algorithm to {\tt\small Java}. Issues
related to subtyping of recursive types are also discussed.
