This document provides an introduction and overview of the British Pharmacopoeia (BP), British Pharmaceutical Codex, United States Pharmacopoeia-National Formulary (USP-NF), Extra Pharmacopoeia (Martindale), and The Merck Index. It describes the origins, contents, and purpose of each compendium for establishing drug standards. The BP, USP-NF, and Martindale set mandatory standards for active substances and formulated preparations. The British Pharmaceutical Codex provides additional information on drugs and preparations not included in the BP. The Merck Index is a reference work for information on chemicals, drugs, and biologicals.