Synopsis "The present work is based on the material collected from the different habitats of these islands by the authors and various survey parties of Z.S.I. The material studied and reported upon in the present account includes 2532 specimens belonging to 539 species from all the available habitats of the freshwater and marine environments in the A & N Islands. Of these 53 species indicated by asterisk (*) are recorded here for the first time from these islands. The following account includes key to families and taxonomic descriptions, habitats, distribution, etc. of the species encountered and key to distinguish them. The diagnostic features given are based on the specimens collected from the islands and studied by the authors, which have been listed under material examined in the text. Unless otherwise stated, the length of specimens given is total length. Only original bibliographic citation followed by important latest references pertaining to each species is given though several standard publications have been consulted for proper indentification and information on the distribution. The classification of fishes followed here is that of Nelson (1984), Smith and Heemstra (1986) and other revisionary works. A comprehensive bibliography of taxonomic descriptions or records of fishes reported from the Andaman and Nicobar Islands has been provided. A complete list of species, so far reported with taxonomic description from the islands which are not included in the text, is also provided (Annexure-I). All the material studied has been deposited in the reference collections of Zoological Survey of India at Port Blair."