The paper summarizes the results of a long-term study on the ecology of Dreissena polymorpha (Pall.) in several dozen lakes of different size, depth and trophy. The abundance of adults, planktonic larvae, and settled postveligers was found to vary widely between the lakes, localities within a lake, and years. The temperature influences the period of appearance and abundance dynamics of planktonic larvae; wind affects their vertical and horizontal distribution in the water column; winds and water currents displace settling postveligers. Settling postveligers display preferences for various natural substrates: most often they settle on submerged plants, especially perennials. The age structure of D. polymorpha settled on plants (dominance of young individuals, at most 3 years old) differs from that in colonies settled on the littoral bottom. The abundance of mussel populations in lakes is primarily determined by the mortality at the transition from planktonic to sedentary life, and by the mortality of individuals settled on submerged plants.