The Investigator's Brochure (IB) is a multidisciplinary document that summarises the main elements of an entire development programme to date. Although the IB also serves other purposes, it is primarily written to enable investigators conducting clinical studies to assess the risks and benefits associated with an investigational product. The ICH E6 guideline specifies that an IB should include information on the investigational product itself as well as on its use in non-clinical and clinical studies, together with a section providing guidance for the investigator on the use of the drug. Beyond a need for good project management skills, the main challenge and responsibility for medical writers is to ensure that the information presented in an IB is as concise and focused as possible while remaining balanced and sufficiently complete to communicate what an investigator needs to know about using the investigational product.