Abstract: Studies on attached algae communities, collected from artificial substrates, were made in upper and middle reaches of Tumen River in 1977—1979. Bioassay using Scenedesmus for some effluents was carried out in laboratoty.Based on results obtained, evaluation of water pollution in the River was made. The upper reach, represented by station Chongshan, is evaluated as unpolluted area. The middle reach, from the drainage of iron-ore mining effluents downwards to station Xiangrenpingheavily to moderately polluted area. From station Caidui, where the River receives the pulp mill effluent, to city Tumen, the river water is most heavily polluted. The stretch of River between station Hedung and the pollution source of a brown-coal chemical industry in the lower reach is considered as slightly to moderately polluted.Bioassay tests also show that pulp mill effluent is one of the main pollution sources of River Tumen. The acute ILm of Scenedesmus to the main sewer effluent of the pulp mill is about 45% (v/v). The most toxic is the sulfite waste liquor. The harmful effect on algae growth by iron-ore mining effluent is caused by the large amount of suspended solids contained in this effluent, which reduces photosynthetic activity of algae. This effluent must be considered as another main polhution source of the River.Discussing and comparing the results of periphyton studies in Tumen River, the authors propose some algological indices: for monitoring and evaluating pollution conditions: in this river. Among them the total count of attached algae is the most suitable and is expressed as a comparable relative value. Some indicator algae species are presented. The application of diversity indexes is discussed.