The Common Technical Document (CTD) is a set of specification for application dossier for the registration of Medicines and designed to be used across Europe, Japan and the United States. It is an internationally agreed format for the preparation of applications regarding new drugs intended to be submitted to regional regulatory authorities in participating countries. It was developed by the European Medicines Agency (EMA, Europe), the Food and Drug Administration (FDA, US) and the Ministry of Health, Labour and Welfare (Japan). The CTD is maintained by the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH).
The complete name of ICH is the "International Conference on harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use". ICH is a joint initiative involving both regulators and research-based industry representatives of the European Union, Japan and the USA in scientific and technical discussions of the testing procedures required to assess and ensure the safety, quality and efficacy of medicines. The goal of ICH is to promote international harmonization by bringing together representatives from the three ICH regions (EU, Japan and USA) to discuss and establish common guidelines. For example, since year 2003, the authorities in the United States, the European Union (EU) and Japan ask for the Common Technical Document (CTD) format set out by the 2003 International Conference on Harmonization (ICH) which was agreed by the Regulatory Agencies of Europe, Japan and the US and the Research-based Industryand more recently, its electronic version - the electronic Common Technical Document(eCTD). CTD provides a common format for the submission of information to the Regulatory Agencies for the registration of the pharmaceutical product.
The CTD is organized into five modules region specific and intended to be common for all regions.
The agreement to assemble all the Quality, Safety and Efficacy information in the CTD format has revolutionized the regulatory review processes, led to harmonized electronic submission that, in turn, enabled implementation of good review practices.
The Common Technical Document is divided into five modules:

• Administrative and prescribing information
• Overview and summary of modules 3 to 5
• Quality (pharmaceutical documentation)
• Preclinical (Pharmacology/Toxicology)
• Clinical – efficacy (Clinical Trials)

Detailed subheadings for each Module are specified for all jurisdictions. The contents of Module 1 and certain subheadings of other Modules will differ, based on national requirements. After the United States, European Union and Japan, the CTD has been adopted by several other countries including Canada and Switzerland. The Paper CTD is destined to be replaced by its electronic counterpart, the eCTD.
References:
"Guidance for Industry, ICH M4: Organization of the CTD" U.S. Department of Health and Human Services Food and Drug Administration Center for Drug Evaluation and Research (CDER) Center for Biologics Evaluation and Research (CBER) August 2001