An integrated investigation of the community structure and growth potential of algae in Taipinghu Reservoir, Anhui Province, China, was conducted from July 1993 to October 1994. A total of 112 algal species belonging to eight phyla were observed. Green algae were the dominant population, representing 55% of the total recorded taxa. Diatoms and blue-green algae formed the second and the third largest algal groups, respectively. The total species and population of algae were relatively steady in spring, summer and autumn, but exhibited some variety in winter. Compared to earlier data, the species richness decreased by 36% and the number of genera decreased by 23% over an eight-year period. The maximum values of the annual mean cell count, biomass and chlorophyll a concentration appeared in summer and the minimum in winter. The algal growth potential of the original water without supplemental nutrients was much lower than that of the control culture, but equal to or a little higher than the control culture which was supplemented with complete nutrients. The study results imply that phosphorus is the limiting nutrient for algal growth and that the trophic status of the reservoir is changing from mesotrophic to eutrophic. Based on these data, some advice on how to manage the reservoir is offered.