Cycloate (S-ethyl N-ethylthiocyclohexanecarbamate), applied by subsurface injection at 3.4 kg/ha, controlled 98 to 100% of barnyardgrass [Echinochloa crus-galli (L.) Beauv.] and 82 to 94% of common lambsquarters (Chenopodium album L.) and hairy nightshade (Solarium sarachoides Sendt.). Phenmedipham (methyl m-hydroxycarbanilate m-methylcarbanilate) at 1.1 kg/ha, applied after sugarbeets had emerged but before common lambsquarters had more than three pairs of true leaves or hairy nightshade had more than three or four true leaves, controlled the members of these species that had survived cycloate. Cycloate preconditioned sugarbeets and the surviving broadleaf weeds to injury be phenmedipham. Although applying phenmedipham following cycloate before sugarbeets had two pairs of true leaves sometimes resulted in severe crop injury, and applying it when weeds were too large resulted in incomplete weed control, in all experiments there was a period of at least 2 weeks during which application of phenmedipham killed the surviving lambsquarters and nightshade without injuring sugarbeets.