In recent years many organisations have been moving to the use of object-oriented methods for the development of information systems. Many claims have been made about the efficacy of object-oriented methods for specifying and building software and information systems. Several studies have looked at small groups (often students) using object-oriented methods for small one-off exercises or problems. These studies lack information about how real systems are being developed in practice. There is a need to investigate the use of object-oriented methods by practising professionals in the production of requirements specifications for "real world" sized projects. In this paper firstly we outline a conceptual framework of "what might be happening" in professional object-oriented requirements engineering based on the common characteristics of published, well known objectoriented methods. Secondly, we describe a research plan for a set of case studies that are currently being undertaken.