OBJECTIVES: To evaluate and determine the value of monitoring models developed by the Mahidol Oxford Tropical Research Unit and the East African Consortium for Clinical Research, consider how this can be measured and explore monitors' and investigators' experiences of and views about the nature, purpose and practice of monitoring. RESEARCH DESIGN: A case study approach was used within the context of participatory action research because one of the aims was to guide and improve practice. 34 interviews, five focus groups and observations of monitoring practice were conducted. SETTING AND PARTICIPANTS: Fieldwork occurred in the places where the monitoring models are coordinated and applied in Thailand, Cambodia, Uganda and Kenya. Participants included those coordinating the monitoring schemes, monitors, senior investigators and research staff. ANALYSIS: Transcribed textual data from field notes, interviews and focus groups was imported into a qualitative data software program (NVIVO V. 10) and analysed inductively and thematically by a qualitative researcher. The initial coding framework was reviewed internally and two main categories emerged from the subsequent interrogation of the data. RESULTS: The categories that were identified related to the conceptual framing and nature of monitoring, and the practice of monitoring, including relational factors. Particular emphasis was given to the value of a scientific and cooperative style of monitoring as a means of enhancing data quality, trust and transparency. In terms of practice the primary purpose of monitoring was defined as improving the conduct of health research and increasing the capacity of researchers and trial sites. CONCLUSIONS: The models studied utilise internal and network wide expertise to improve the ethics and quality of clinical research. They demonstrate how monitoring can be a scientific and constructive exercise rather than a threatening process. The value of cooperative relations needs to be given more emphasis in monitoring activities, which seek to ensure that research protects human rights and produces reliable data.