The invention provides a process for simultaneously preparing 4,4'-diphenylmethanediamine and diphenylmethane diisocyanate and polyphenylenepolymethylene polyisocyanates, comprising the steps of a) preparing a mixture of diphenylmethanediamine and polyphenylenepolymethylenepolyamines by acidic condensation of aniline and formaldehyde and subsequent workup of the mixture, b) removing a portion of the mixture prepared in step a), c) distilling the mixture removed in step b) in a column, d) recycling the bottom product from step c) to the end product from step a) and condensing the top product from step c), e) distilling the top product from step c) in a column, f) recycling the top product from step e) to the end product from step a), g) recovering the 4,4'-diphenylmethanediamine obtained as the bottom product in step e), h) reacting the mixture from step a) with phosgene and subsequently working up the reaction product.