SUMMARYThis research follows in the Broadbent tradition of constructing a general theory to solve applied problems. The paper reports part of wider research intended to construct a framework for modelling the planning and control of multiple task work. The function of the framework is to support the solution of design problems associated with the performance of interactive planning and control worksystems. The study reported here applied an initial version of the framework, based on a study of secretarial office administration, to construct a model of medical reception work. An observational study collected protocol data concerning a medical reception worksystem -comprising two receptionists and various office devices; its domain of application -comprising doctors, patients, their appointments, medical records etc.; and its performance, comprising the quality of medical reception work and the costs to the receptionists of performing that work. The data were then used in conjunction with the planning and control framework to construct the model of medical reception. The model includes physical and abstract structures and behaviours of the medical reception worksystem, as well as physical and abstract objects of its domain of application. Of particular interest for the solution of design problems is the model's differentiation of plan types into task plans, procedure plans, and activity plans. These plan types were used to extend the framework for the planning and control of multiple task work. The paper concludes with a brief illustration of how the model of medical reception might be used to support the solution of interactive worksystem design problems as they relate to performance. Future work to develop further the framework of planning and control of multiple task work and its application are discussed.