The present invention relates to the preparation of nitrobenzoic acids by oxidizing particular nitrotoluenes, nitrobenzyl alcohols, esters and/or ethers in the presence of nitric acid at elevated temperature and elevated pressure. It has been found that the particular nitrotoluenes, nitrobenzyl alcohols, esters and/or ethers may be oxidized particularly reliably and in high yields using nitric acid to the benzoic acid derivatives when they are metered into the nitric acid.