Paranthias colonus(Valenciennes, 1846) is used as fish bait replacing first class fish that have been overfished in the Gulf of California. Due to its recent commercial importance, the parasite fauna of P. colonusfrom of El Sargento, Baja California Sur, Mexico is characterized to define its role in the life cycle of its parasites. 30 fishes were fixed in 4% formaldehyde for later examination. Helminths and copepods were treated with conventional techniques specific to each kind of parasite. P. colonushad 100% prevalence and 46.5 mean intensity of parasites. Adults of Pseudorhabdosynochus sp., Prodistomum orientalis, Brachyphallus sp., Lecithochirium sp., Spinitectus sp., Caligus sp., Pandaridae, and Hatschekia sp. and larevae of Tetragonocephalidae, Scolex pleuronectis and Anisakis sp. were found. There was evidence of host specificity of Pseudorhabdosynochussp. and Hatschekiasp. by ser...