A challenging question is how XML can be used to support distributed databases. This leads to the problem of how to obtain a suitable, cost-efficient distribution design for XML documents. In this paper we sketch a heuristic approach to minimise query costs for the case of horizontal fragmentation. The approach is based on a cost model that takes the complex structure of queries on XML documents into account. We show that the minimisation of transportation costs is decisive, and that this can be achieved locally by either accepting or rejecting a horizontal fragmentation with a simple predicate that arises from one of the most frequent queries.