Aspochalamins A-D, a family of new cytochalasan antibiotics have been isolated from Aspergillus niveus, an endosymbiotic fungus isolated from the gut of a woodlouse belonging to the family Trichoniscidae. Besides aspochalamins, aspochalasin Z, a new member of the aspochalasin family, as well as the known mycotoxins aspochalasin D and citreoviridins A/C and B were isolated from the mycelium. Aspochalamins showed cytostatic effects towards various tumor cell lines and a weak antibacterial activity against Gram-positive bacteria.