Fungi play a considerable role for the deterioration of cultural heritage. Due to their enormous enzymatic activity and their ability to grow at low aw values fungi are able to inhabit and to decay paintings, textiles, paper, parchment, leather, oil, casein, glue and other materials used for historical art objects. The weathering of stone monuments is significantly increased by epi- and endolitic fungi. In museums and their storage rooms, climate control, regular cleaning and microbiological monitoring are essential in order to prevent fungal contamination. Education and close collaboration of mycologists and restorers are needed to develop object specific methods for the conservation and treatment of contaminated objects.