Controversy exists regarding the ethics of using placebo control groups in clinical trials when effective treatments exist. The debate was fueled by the announcement of the 5th revision of the Declaration of Helsinki (2000). This study reviews the history and scientific background surrounding the controversy and investigates the prevailing attitudes of Hong Kong researchers regarding this issue. The controversy has centered on a few issues. The first involves the methodological superiority of placebo-controlled trials in discerning treatment effects. Secondly, it is unclear if the treatment effects encompass absolute treatment effects (including placebo effects) or are confined to treatment-specific effects (excluding placebo effects). Thirdly, there are worries that subjects in the placebo group could be exposed to higher risk for developing serious adverse events. Fourthly, it is debated whether the standard of best available treatment should be a local one, or an international one. Preliminary research findings suggest that the opinions of the Hong Kong researchers seemed to be divided on the use of placebo control groups in clinical trials when effective treatment exists. Further researcher on the topic is therefore warranted, training and consensus meeting may be necessary to minimize the confusion related to this issue.