The scientific lecture with the title of "Benthic invertebrates in the rivers of Gilan Province" was presented by Mr. Ahmad Ghaneh in the conference hall of the National Inland Water Aquaculture Institute on Sunday, August 23, 2020. In this seminar, macrobenthic invertebrate fauna of 21 rivers in the Gilan province from the Astara County in the westernmost region to the Chabaksar city located in the easternmost part of the province were reviewed. Macrobenthic samples were collected from two sampling sites, one downstream and the other at the highest available point. The population characteristics of macrobenthic invertebrates were calculated. According to the population characteristics of macrobenthic invertebrates such as total diversity, diversity of sensitive groups and Shannon diversity index as well as Hilsenhoff biodiversity index, these rivers were compared qualitatively. Accordingly, the rivers of the western basin, Agh Chai River, Chelavand River, Lamir River, Khotbeh Sara River and Haviq River in the upstream areas were of relatively good quality, whereas the rivers in Dinachal, Khaleh Sara, Lavandvil and Choobar were of relatively low quality. The Choobar (Shaft) River from the Anzali wetland basin has a much better quality than other rivers in this basin. Also, the Siah Mazgi River has very favorable conditions upstream and then Chafroud River is another river with good quality. The Gasht-e Rudkhan River and Morghak River were of much lower quality. In the Sefidrud basin, the Zalaki Rud Khan River has very good quality conditions in the upstream areas, whereas the Siyahrud River is one of the weakest rivers in terms of water quality.