Radioimmunoassays for chlorinated dibenzo-p-dioxins, -bipheyls, and -dibenzofurans have been developed, as has a radioimmunoassay for mono-2-ethylhexyl phthalate in plasma. Development of a radioimmunoassay for 2,4,5-trichlorophenoxyacetic acid has encountered unexpected difficulties. A contract effort for validation and refinement of these procedures has been initiated.