Evaluating large scale health information systems: from practice towards theory.

With the introduction of large scale health information systems which are incrementally developed from legacy systems, evaluators are faced with difficult methodological and practical problems. Some of the problems involved in multidisciplinary multi-method evaluations care discussed. It is argued that the development of a framework for evaluation is necessary in order to successfully plan an evaluation, understand the implications of the results and make future predictions based upon them. Some suggestions for arriving at such a framework are put forward.