A process for the preparation of 2,3,4,5,-tetrafluorobenzoic acid of the formula (1) ##STR1## by heating N'-substituted N-aminotetrafluorophthalimides of the formula (2) ##STR2## in which X is the radical ##STR3## where R.sub.1, R.sub.2 are a hydrogen atom, an alkyl-(C.sub.1 -C.sub.10)- group, aryl group, alkyl-(C.sub.1 -C.sub.6)-Co- group or aryl-CO- group, it being possible for the aryl or aryl-CO- group in the case of R.sub.1 and R.sub.2 to be substituted on the aromatic ring by fluorine and/or chlorine atoms and/or alkyl-(C.sub.1 -C.sub.4)-groups, or R.sub.1 and R.sub.2 together are a phthaloyl radical which can be substituted on the aromatic ring by 4 chlorine atoms or 4 fluorine atoms, or where X is the radical ##STR4## which can be substituted on the aromatic ring by fluorine and/or chlorine atoms and/or alkyl-(C.sub.1 -C.sub.4)- groups, in an aqueous medium at pH values of approximately -1 to approximately +1 at temperatures of approximately 160 to approximately 220.degree. C.