This paper summarizes the results of long-term research concerning the algal biodiversity of some mountain lakes in the Eastern Black Sea region of Turkey. The algal flora is comprised of 182 taxa from four divisions: Cyanophyta (24), Bacillariophyta (80), Chlorophyta (76) and Euglenophyta (2). The taxonomic composition of the algal flora has been analysed. Differences between the communities of the studied lakes are described and rare taxa are noted. The algal flora of the mountain lakes in the Eastern Black Sea region is more diverse than those of other lakes studied in Turkey.