Merck Manual of Diagnosis and Therapy

The Merck Manual of Diagnosis and Therapy, referred to as The Merck Manual,^[1] is the world's best-selling medical textbook,^[2] and the oldest continuously published English language medical textbook.^[3] First published in 1899, the current print edition of the book, the 20th Edition, was published in 2018. In 2014, Merck decided to move The Merck Manual to digital-only, online publication, available in both professional and consumer versions; this decision was reversed in 2017, with the publication of the 20th edition the following year.^[4] The Merck Manual of Diagnosis and Therapy is one of several medical textbooks, collectively known as The Merck Manuals, which are published by Merck Publishing,^[5] a subsidiary of the pharmaceutical company Merck Co., Inc. in the United States and Canada, and MSD (as The MSD Manuals) in other countries in the world. Merck also formerly published The Merck Index, An Encyclopedia of Chemicals, Drugs, and Biologicals.