Enterprise models, based on the responsibilities and relationships underlying market activities, are used to provide a framework for representing and analysing the activity of brokerage in network-based commerce. Examples of models are presented that represent new configurations of systems, services and processes. Three distinct phases of brokerage are recognised: rendezvous, transaction and post-sales. The security requirements for transactions in broking are so much greater than those for information provision over the Internet that separate business cases can be made for each.