The dimethylamine salt of 2,4-DB [4-(2,4-dichlorophenoxy)butyric acid] combined with toxaphene (chlorinated camphene) or acifluorfen [5-(2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenzoic acid] and toxaphene combined with acifluorfen at several rates each were applied in the greenhouse and field to sicklepod (Cassia obtusifolia L.) to determine interactions. Toxaphene plus 2,4-DB treatments produced synergistic or additive responses in the greenhouse and in the field. Antagonistic or additive responses were observed with acifluorfen plus 2,4-DB treatments in the greenhouse, but not in the field. Acifluorfen plus toxaphene produced only additive responses in the greenhouse with synergistic interactions observed under field conditions.