Ambiphryosis of fishes is invasion disease of fry of American catfish, carp, grass carp (Clenopharyngodon idella), silver and particoloured carp, and buffalo. This fish disease is characterised by the destruction of the morphology of the tissue cells and their functions – respiratory, secretory and excretory, exhaustion and death of fishes. The document consists of 5 Secs. Section 1 lays down general provisions. Section 2 regards epizootology. Section 3 regards clinical symptoms and pathogenesis