Polyclonal antibodies raised against 6,7‐dihydro‐6‐carboxyaldrin can be used to detect aldrin and dieldrin. These analytes are preferentially fat soluble. An immunoassay is described which provides a method for detecting these pesticides in milk, a fat‐rich matrix. The enzyme‐linked immunosorbent assay (ELISA) can detect aldrin/dieldrin in milk in the range 1 ng ml‐1‐5 μg ml‐1simply and reliably. The detection range differs in skimmed and semi‐skimmed milk and in cream, reflecting the differences in fat content between these samples.