Large and complex software systems contain a variety of entities (objects) and a complex control system (transformation function). The pure object-oriented design and structured design approaches concentrate on either objects or the transformation function separately. As such they may not be adequate in isolation, to deal with the design of complex systems. Therefore, it makes sense to study their combination. We propose a combined functional and object-oriented design approach (CFOOD) based on the extended object-oriented design method proposed by P. Jalote (1989, 1991). The CFOOD approach makes full use of the object-oriented design and structured design techniques combining the object view and the functional view to provide a more complete view of a system. We demonstrate the use of our approach by a design example of a hospital patient monitoring system.