This guidance on statistical principles drafted by the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH), is written primarily to attempt to harmonise the principles of  statistical methodology applied to clinical trials for marketing applications submitted in Europe, Japan and the United States. This document on statistical issues related to clinical trials underlines the role of statistics in clinical trial design and analysis. The focus of this guidance is on statistical principles. It does not address the use of specific statistical procedures or methods.