The discharge of large amounts of organic and inorganic materials accelerates the eutrophication process of the lagoon. In order to provide some of the required information for restoration programs of the lagoon , its trophic state, from the stand of chlorohyll - A, tot al phosphorus and tot al nitrogen have been studied, applying remotely sensed data and GIS. The result s of a study on 3 limnological factors through 1991 - 1994 in 36 stations in Anzali lagoon were entered in a GIS. A map of this lagoon is prepared by means of digital Landsat TM - data. After examining thei r goemetric and radiometri c qualit ies, geometric registr ation and suitable enhancement were done. The satell ite images were interpreted visually on computer display. According to this interpre tation the area of lagoon' measures to 141 square kilometers. After locating all 36 sta tio ns on a layer, all factor s were interpolated to the entire lagoon area weighted inter polation. The trophic states concerning to chlorophyll - A, total phosphorus, tot al nitrogen and their indices (Carlson, 1996) were determined. The result s have shown that about 75% of the lagoon is eutrophic and 25% lies in mesotrophic range. The comparison between the OECD (1982) standards and the normal distribution curve of tot al phosphorous indicates that this lagoon is passing the end stages of eutrophy and tends to turn into hypertrophy. Several internal and external factors have caused the accleration of eutrophic process. Therefor e, the monitoring programs within the aquatic environments and the control of eutrophic factors within the catchment area are necessary for decreasing the nutrient load of the lagoon.