Compartive studies of species diversity indices in marine benthic communities were made from pollution survey data in the upper gulf of thailand form 1974-1976mthe areas compared were the northwestern coastline form sakhon province to petchaburi province (area a), the northeastern coastline form samut prakan province, ko sichang to laem chabang in chonburi province (area b),the western coastline form area a on down to hua hin in prachuap kiri khan province (area c) and the eastern coastline form area b to ko juang in rayong province (area d). the average species diversity index in the northwestern coasiline was found to be lovest at 0.379.