Operational Research models are well established as an effective tool for tackling a vast range of health care problems. Many of these models involve parameters which depend on human behaviour, and thus individuals' characteristics or personality traits should be included. In this paper we describe a discrete event simulation model of attendance for screening for diabetic retinopathy, a sight-threatening complication of diabetes. This model takes into account the physical states, emotions, cognitions and social status of the persons involved. The model also uses some ideas from the discipline of health psychology. We believe that this approach provides what is potentially a far more accurate method of modelling patients' attendance behaviour, compared with the standard approach of simple random sampling of patients. However, further empirical work is required, firstly to derive and validate more realistic forms of the model equations, secondly to select the appropriate psychological variables, and thirdly and inevitably to collect data. (C) 2002 Elsevier Science B.V. All rights reserved.