Sexually mature white perch (Morone americana), brought into Nebraska in the spring of 1964, spawned successfully in hatchery ponds. Some of the progeny were stocked in several of the highly alkaline lakes in the Nebraska Sandhills while others were inadvertently introduced into a turbid flood control reservoir in southeastern Nebraska. The species became established in the reservoir where it made very rapid growth and achieved sexual maturity one to two years sooner than in its natural range. Over a three year period the white perch completely displaced the native black bullhead as the dominant species in the reservoir. This dominance is being maintained and the white perch population is becoming stunted. During periods of reservoir discharge in the spring large numbers of white perch escape through the spillway. The stream on which the reservoir is located is tributary to the Platte River which subsequently joins the Missouri River. There appears to be no barrier to the movement of white perch through this stream system to the Missouri as they have been captured throughout the system up to a point only 18 stream miles from the juncture of the Platte and Missouri rivers. It appears likely that many white perch have successfully made the journey. The future prospects of the species in the Missouri River should be interesting.