This paper describes the theoretical and methodological perspectives adopted by a multidisciplinary research group undertaking a government-funded evaluation of a United Kingdom innovation in the continuing care of elderly people. In 1983 three experimental National Health Service (NHS) nursing homes were set up to care for patients usually cared for in NHS geriatric hospitals. Drawing on different approaches to the evaluation of health-care innovations, this paper delineates an evaluation model which identifies four types of variables: structure, process, intermediate outcome and final outcome. The relationship of this model to the design of an evaluation comprising seven complementary research activities is described, emphasising the need for multiple perspectives and multiple methods in policy-oriented health-care evaluations.