Background: Although ethics consultation has been introduced to clinical practice for many years, the results of empirical studies to evaluate the effectiveness of ethics consultation are still controversial. The design of randomised controlled trials is considered the best research design to evaluate the effect of a clinical practice on the outcomes of interests. In order to understand the effects of ethics consultation, we conducted this search for studies with the design of randomised controlled trials to evaluate ethics consultation.Objective: To provide (...) an integrated review of studies with the design of randomised controlled trials to evaluate the effectiveness of ethics consultation.Methods: PubMed was used to search for studies using the randomised controlled trial design to evaluate the effectiveness of ethics consultation. The search term used was “ethics consultation”. The selection criterion was limited to “randomised controlled trial”.Results: Four articles that met both search criteria were retrieved. One of these articles reported a study that did not actually use the design of a randomised controlled trial and is excluded from the following discussion.Conclusions: To apply randomised controlled trials to evaluate the effectiveness of ethics consultation is extremely difficult as long as two issues are not resolved: the standardisation of ethics consultation and a placebo for ethics consultation to eliminate the placebo effect. Thus, the results generated by the design of randomised controlled trials are always problematic. Furthermore, as long as the two issues exist, the results generated by the design of quantitative research methods always pose problems. (shrink)