Aims: This paper reviews placebo and placebo effects and their measurement and application to nursing. Ethical and methodological issues are also discussed. Implications for nursing and recommendations for future study are offered. Background: Placebos have been used for decades in clinical trials but discussion about conceptual, methodological and ethical issues has been comparatively scarce. Conclusion: It is concluded that true placebo effects are difficult to measure and control and the use of credible placebo is sometimes impractical in clinical nursing research. This leads to the increased use of usual care as a control by researchers. However, more information should be reported in studies that use this approach, including the specification of usual care, its monitoring and patient adherence. Relevance to clinical practice: Where its use is considered ethical, safe and feasible, a placebo arm should be included in studies of efficacy to distinguish between active and inactive treatment.