Abstract: Inventory, diversity and community structure of aquatic arthropods between weeded and partially weeded rice ecosystems were studied in a field experiment under irrigated condition during Rabi, 2000. The research revealed that a total of 12, 2, 6 and 3 species of Odonata, Ephemeroptera, Hemiptera and Coleoptera aquatic insects were recorded, respectively. Agriocnemis femina femina Brauer of damselfly, Pantala flavescens (Fabricius), Crocothemis servilia (Drury) and Diplocodes trivialis (Rambur) of dragonflies were the dominant species in both the ecosystems, but were significantly more dominant in partially weeded rice ecosystem. Trithemis sp., Rhyothemis variegata (Linnaeus), Anax guttatus (Burmeister) of dragonfly and Lethocerus indicus (Lepeletiller + Serville) (Giant water bug) were absent in weeded rice ecosystem and rest of the species occurred in both the ecosystems. Aquatic beetles, water strider and water scorpion evinced perfect similarity through out the season. But, damselfly, backswimmer and mayfly expressed more than 0.80 similarity and perfect similarity (1.00) during early and maturity stages of crop and showed less stability during the 2nd, 3rd and 4th week. The guild of aquatic arthropods revealed the dominance of predatory groups in partially weeded rice ecosystem through out the season. Same group of aquatic arthropods had not dominated in all the weeks of crop growth, but the group of aquatic arthropods changed during various stages of crop. A total of 18 weed species were recorded in partially weeded plots.