The rate of impingement of fishes on the vertical traveling screens at Peach BottomAtomic Power Station Unites No. 2 and 3, Pennsylvania, was determined from November 1973through December 1975. At unit No. 2, 14,383 specimens (157 kg) of 33 species were impingedin one hundred seventy four 12-h sampling periods. AT unit no. 3, 40, 0046 specimens (1,153 kg)of 33 species were impinged in seventy-one 12-h sampling periods. Channel catfish, (Ictaluruspunctatus), white crappie (Pomoxis annularis) and bluegill, (Lepomis macrochirus), wereimpinged most frequently. Impingement was highest in November through April. Impingementwas highest during the start-up phase of each unit. Multiple regression analysis revealed that theintake water temperature, daily river flow, and pond elevation accounted for 32 to 73 percent ofthe variation in the impingement of fishes. Winter (January through March) mortality of whitecrappie and bluegill at the screens was equal to that caused by a few anglers over the sameperiod. The design and placement of the screens, preceded by relevant behavioural studies were,in part, responsible for minimal fish losses due to impingement at Peach Bottom.