Interoperability between ICT systems is becoming an increasingly important success factor in the cooperation of enterprises. Organisations have to exchange business information and must have the same understanding of the meaning of the exchanged information. Only then can they rely on both the transaction of the information and the validity of its contents. This paper reports on the European INTEROP Network of Excellence concerned with interoperability research for networked enterprises applications and software, its goals, rationale and early results. In addition, an application of interoperability in a supply chain network of SMEs is presented and discussed.