The purpose of this study is to evaluate the benthic macroinvertebrate distribution in the Keºap Stream (in the Eastern Black Sea Region of Turkey) for the summer period using biotic index. The water quality was assessed through the application of the Belgian biotic index. For this purpose, benthic macroinvertebrate sampling was performed in six sites along the Keºap Stream in the summer period, in July 2007. The distribution of dominant genera of the sites was evaluated according to water quality. According to the Belgian biotic index, II, III and IV water quality classes (slightly, moderately and heavily polluted, respectively) were determined in the stream. In addition, diversities of benthic macroinvertebrates in six sites were calculated. The biotic index values are found also consistent with the diversity values. Especially, in areas of the stream after industrial facilities water quality decreased. However, very heavy pollution was not observed accord to the biotic index values. It was found that Ephemeroptera was the dominant major taxon in all sampling sites. As a result of this biological evaluation, Ephemeroptera were concluded to be the most common taxa in the stream and the ephemeropterans, Potamanthus, Baetis and Ephemerella were dominant genera in the conditions of slightly, moderately and heavily polluted.