Many quality improvement interventions such as educational programmes, hospital quality strategies, and quality evaluation systems have not been evaluated. The aim of this paper is to encourage research into these "quality improvement processes" by presenting suitable designs and methods, and by describing research approaches which are less familiar in healthcare. The paper proposes that the choice of research design depends on the level and complexity of the intervention. Theory-building approaches are more suitable than experimental theory testing approaches for evaluating higher-level complex interventions and for understanding critical context factors. Collaborative action evaluation studies can provide useful information for decision makers--an examples is given. "User focused" research can provide knowledge for developing more effective quality intervention processes and for making better decisions about their use and implementation.