The aim of this diploma thesis is to introduce the notion of ugliness as an aesthetic category, concerning the question of its position in the aesthetic experience, based in particular on the conception of difficult beauty by Bernard Bosanquet. The first part of the thesis discusses the possibility of aesthetic experiencing of unpleasantness and so specifies ugliness as inherently aesthetic category, in comparison to the unaesthetic response of disgust. The second part of the thesis deals with the question of position of ugliness and the feeling of unpleasantness if ugliness is an adequate part of the aesthetic experience which is regarded as excellent and contributing. The solution offered by Bosanquet in his conception of difficult beauty however isn't fully sufficient and therefore the last chapter introduces the problem of ugliness from a different viewpoint which emphasizes the negativity and disturbance of ugliness, impossible to dissolve. The key feature of ugliness is the ambivalent link amongst the repulsion and the attraction in aesthetic experiencing. The attribution of a meaning in the whole of the aesthetic experience, i.e. the possibility of attaining new insight thanks to ugliness, may however lead to a tendency to the reconciliation of ugliness. The original unpleasantness and...