This paper compiles information on various aspects of the biology (i.e., taxonomy and morphology, geographical distribution and occurrence in relation to salinity, hosts, attachment sites, occurrence on wild and captive hosts, occurrence in plankton samples, life cycle, pathogenicity, and treatment and control) of the caligid copepod Caligus epidemicus based on the literature published in 1971?2013. The species attaches to the body surface of fish; it exhibits very low host specificity and has been found from 36 teleost species in 17 families and 5 orders and even from cultured shrimps. It is the most pathogenic parasite among the known caligid copepods from the Indo-West Pacific region, causing mortalities in captive fish as well as disease problems in wild and captive fish. Its infection level remains low in wild fish populations, but fish in captivity usually have higher levels of infection than those caught in the wild. Its life cycle was reported to comprise 10 stages (two naupliar, one copepodid, six chalimus stages, and adult) although Caligus spp. have typically eight stages in their life cycles. A rearing period of 17 days at 24?25oC is necessary for the species to develop to an ovigerous female after hatching from the egg.