The invention relates to a process for working up alkaline waste water which is formed during washing of crude nitrobenzene obtained by nitration of benzene, wherein (i) the alkaline waste water is heated under an increased pressure with respect to atmospheric pressure with exclusion of oxygen and is then cooled and expanded; (ii) the waste water obtained in (i) is purified further by stripping with a stripping gas and the stripping gas stream loaded with impurities is then cooled to a temperature of from 10° C. to 60° C.; and (iii) the liquid process product obtained in (ii) by cooling the stripping gas stream loaded with impurities is separated into an aqueous and an organic phase and the organic phase is used further in an aniline production process.