Carl Fredrik Adler, a teacher of linen, was a surgeon with the Swenska Ost-Indiska Compagniet. During the company's longest completed expedition 1753-1756, he kept a ship's doctor's journal of all his patients, unique in its detail, also containing vivid descriptions of life on board. This document has since been kept and handed down within the family, but has otherwise been completely unknown. A few years ago, the then owner of the document made contact and expressed his wish that it be published. The transcription of the handwritten journal has now been completed, along with extensive additional work with informative text chapters and explanatory lists, and the entire manuscript is ready for publication. Adler's journal is a unique document in the history of medicine. It is the oldest known medical document of Swedish origin that describes in detail the diagnosis, treatment and prognosis of patients in the mid-18th century and covers more than 200 different cases of illness. Corresponding documents from 18th-century Swedish hospitals appear sparse in terms of content compared to Adler's journal.