Peregrine Falcons (Falco peregrinus) captured in the spring at Padre Island, Texas, nest across the arctic and subarctic from Alaska to Greenland and winter throughout Latin America. Padre Island, located immediately north of the Mexican border, is the peregrines' first landfall in the U.S.A. after spending about 6 mo in Latin America. Blood plasma was collected from spring migrants at Padre Island between 1978 and 2004 to monitor trends in organochlorine (OC) pesticides and their metabolites. Geometric mean concentrations of p,p'-DDE (??g/g, ww) decreased throughout the study: 1978-1979 (0.879), 1980 (0.617), 1984 (0.551), 1994 (0.406) and 2004 (0.013). Most other OC pesticides, with detection limits used during the earlier portion of this study, were no longer detected during the last two sampling periods. The reduced concentrations of OC pesticides suggest that other pesticides (including carbamates, organophosphates and pyrethroids) are likely being used as replacements. These replacement compounds are not as persistent and cannot be readily evaluated at migration sites like Padre Island. However, concentrations of flame retardants (polybrominated diphenyl ethers; PBDEs) have recently increased in bird eggs in many regions and have been reported in blood plasma. Concentrations of PBDEs in peregrine plasma could be evaluated at Padre Island for assessment of trends in the Americas. ?? 2009 The Raptor Research Foundation, Inc.