Effects of 22 herbicides on the ATP content of excised soybean [Glycine max (L.) Merr., var. Lee] hypocotyls were determined and compared with interferences reported previously on RNA and protein syntheses. Herbicides that reduced ATP levels and inhibited RNA and protein syntheses were 2-sec-butyl-4,6-dinitrophenol (dinoseb), 4-hydroxy-3,5-diiodobenzonitrile (ioxynil), 3′,4′-dichloropropionanilide (propanil), isopropyl m-chlorocarbanilate (chlorpropham), 2,3,5-trichloro-4-pyridinol (pyriclor), 2-chloro-N-isopropylacetanilide (propachlor), (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), and (2,3,6-trichlorophenyl)acetic acid (fenac). No herbicide was found which reduced tissue ATP levels, but did not inhibit RNA and protein syntheses. The correlations established between tissue ATP levels and inhibition of RNA and protein syntheses suggested that interference with the production of energy, required to drive the biosynthetic reactions, could be the mechanism through which these herbicides expressed their effects.