Trifluoromethyl-substituted biphenylcarboxylic acids are prepared by converting methyl-substituted biphenylcarbonitriles into the corresponding trichloromethyl-substituted biphenylcarbonitriles, converting the trichloromethyl group thereof to a trifluoromethyl group and thus obtaining trifluoromethyl-substituted biphenylcarbonitriles, and preparing the corresponding carboxylic acids therefrom by hydrolysis. A number of intermediates arising during this are novel compounds.