Concern has been expressed that the extensive use of organochlorine pesticides in California may be exposing waterfowl to hazardous contaminant levels. The objectives of this study were to determine concentrations of organochlorines in northern pintails (Anas acuta) from 5 important waterfowl wintering areas in California, compare concentrations of organochlorines in selected species with emphasis on relationships to their diets and to determine the relationships between concentrations of organochlorines in wings and carcasses of pintails. In the 1980-1981 hunting season, wings of pintails, canvasbacks (Aythya valisineria) and lesser scaups (A. affinis) were obtained from the Pacific Flyway survey of waterfowl productivity, and additional pintails and northern shovelers (Anas clypeata) were collected in Sacramento Valley. Concentrations of all compounds in pintail wings were below 1 ppm (wet weight), but residues were higher in wings from pintails shot late in the hunting season than early in the season, suggesting that accumulation of chemicals occurs while ducks are wintering in California. Highest concentrations were found in pintails from the southern regions and lowest in those from the northern regions of the state. DDE was significantly higher in males than in females. Wings of diving ducks were too few to enable statistical comparisons. Carcasses of shovelers contained residues of a wide array of organochlorines and significantly (P < 0.001) higher mean concentrations of DDE (0.68 ppm) than did pintails (0.12 ppm) collected at the same time and place. On a wet-weight basis, concentrations of DDE and DDT in the wings of pintails were about half those in the carcasses. Overall, concentrations of organochlorines were relatively low in all species and probably would have no effect on population survival or reproduction. Some individuals, however, contained elevated and possibly harmful levels of certain chemicals.