Service provisioning is at the base of business economy, and a major driver for business-to-business interaction. The strong competition induced by the globalisation of the markets is forcing businesses to concentrate on their core competencies, and to rely on specialised third parties for the provisioning of corollary service infrastructure. New expectations and opportunities are emerging for business uses of the Internet, and value chain optimisation is a priority. The role that the Internet is playing in the business- service market, at the moment revolves around a one- to-one model. Once two businesses have established a relationship, the Internet mainly acts as a communication channel. Efficiency is an important benefit offered by the electronic format of transactions, but very little value is added to the transaction itself. The decision on the best provider for a service and the trust in its capability to deliver the quality expected are instead high-value components for business transactions. Aim of our research is to explore electronic service provision in business-to-business scenarios, focusing on multi- party service composition. A composition-oriented service model has been designed, and it is presented together with the prototype of its support infrastructure. 11 Pages