The author of this chapter started as a ship’s doctor in 1971 and has worked for 9 cruise companies on 22 different ships. He has completed more than 50 ship’s doctor contracts of one week to nine months duration and altogether spent more than 10 years at sea. Rather than evidenced medicine, this chapter is based on the author’s experience and knowledge of common medical cruise line practice. He is a founding member and past board member of the International Maritime Health Association and past chair of ACEP’s Section for Cruise Ship and Maritime Medicine. In his capacity of medical consultant for several cruise companies, he has over the years contributed significantly to some of their medical management manuals and has borrowed extensively from such manuals for this chapter. Other sources are the web-sites of CDC (www.cdc.gov), CLIA (www.clia.org) and ACEP (www.acep.org), as well as own articles in international medical journals and maritime medical newsletters.