Background:Medical research involving human subjects must be evaluated by a research ethics committee before a study is initiated. However, knowledge of REC decision processes, particularly in relation to evaluating the risk–benefit balance in various study types, appears scant.Methods:The study protocols and records of a Finnish university hospital REC were surveyed for a time span of 5 years. All study procedures in each study plan were examined, and the studies were divided into clinical drug trials, clinical trials with medical devices, studies (...) with other invasive interventions, studies with non-invasive physical procedures, and non-physical procedures only.Results:In clinical drug trials, the REC posed queries more frequently about the risk–benefit ratio and less frequently about study methods and participant-related issues in comparison with other study types. Relative to other studies, those with non-physical procedures were subject to more frequent queries related to reliability of the study... (shrink)