An estimated 233 + 16 (95% C.I.) pairs of ospreys (Pandion haliaetus) nested in coastal New Jersey, Delaware, Maryland, and Virginia in 1975. The present populations were considerably smaller than those reported for selected locations at the turn of the century in these four states. The New Jersey population has continued to decline during the last 25 years, although it showed some signs of improved production in 1974-75. The insecticide DDT was used intensively in New Jersey for mosquito control from about 1946 until 1966; its use in the other states was much less intensive, and of shorter duration. In a segment of the pelaware population of ospreys, production was normal and numbers increased slightly in 1970-75. Fragmentary information from Maryland suggests that the number of pairs nesting on duck blinds was about the same in 1958 and 1975. The population in coastal Virginia north of Cape Henry increased from 1970 to 1975. DDE residues in osprey eggs were highest in the areas showing the greatest population declines and the lowest production rates.