The ecological crisis of the Aral Sea has been widely discussed during recent years in both the scientific and popular literature. However, only the consequences of anthropogenic desiccation and increased salinitywere usually discussed with little note of the role played by introduced species in this ecosystem (Micklin, 1991; Williams, Aladin, 1991; Keyser, Aladin, 1991). Here, we review the role of introduced species during periods of varying salinity.