Abstract: A composition of matter for treating warm-blooded animals to eradicate internal parasites comprising a compound chosen from the group consisting of2,4-dibromo-6-nitrophenol2,4-dichloro-6-nitrophenol2-chloro-4-fluoro-6-nitrophenol2-bromo-4-fluoro-6-nitrophenol2-iodo-4-fluoro-6-nitrophenol2-bromo-4-chloro-6-nitrophenolAnd phenolic derivatives thereof and an inert carrier therefor. The composition is particularly useful in killing trematodes or nematodes.

Abstract: A method of killing internal parasites in warm blooded animals comprising administering orally or parenterally to an infected animal an effective amount of a compound of the formula: ##SPC1##Where R.sup.1 is hydrogen or acetyl, R.sup.2 is hydrogen, acetyl or lower alkyl, X.sup.1 and X.sup.2 are iodine atoms; X.sup.3, X.sup.4, X.sup.5 and X.sup.6 which may be the same or different are chlorine, bromine, iodine, trifluoromethyl or hydrogen; at least two and not more than two of X.sup.3, X.sup.4, X.sup.5 and X.sup.6 are hydrogen; when X.sup.3 is chlorine, bromine, iodine or trifluoromethyl, then X.sup.4 and X.sup.6 are both hydrogen; and at least one of X.sup.3, X.sup.4, X.sup.5 and X.sup.6 is trifluoromethyl, said compound being administered in a dosage amount of from 1 to 50 mg active ingredient/Kg animal bodyweight.