Negation is a universal property of human language. Every language has a means to negate a sentence. However, languages vary as to how many different forms they have at their disposal to express sentential negative meaning. Whilst there is only one sentential negative marker in English or Dutch to negate all possible tenses, aspects and moods/modalities (He will/did not walk, He has not walked,... ), some languages have special negative markers, i.e. allomorphs, dedicated to particular tenses, aspects and moods/modalities (TAM). In addition to allomorphy in sentential negative markers, many languages also display various kinds of allomorphy in the marking of TAM, person/gender/number, or the expression of finiteness under the influence of negation. This project wants to investigate whether there is a correlation between the allomorphy observed in sentential negative markers on the one hand, and the allomorphy that is found in other domains under negation on the other hand. With a view to getting a better understanding of the internal structure of negative markers, a typological sample will be investigated to set up a classification of sentential negative markers, focussing on the two directions of allomorphic variation, i.e on how negative markers are conditioned by TAM and how they condition TAM- and other marking.