Stachybotrys atra is often isolated from building materials in houses with moisture problems. Spores of S. atra can contain mycotoxins which may lead to various symptoms in exposed residents in damp houses. The pathogenesis of S. atra-induced lung diseases has not been elucidated. The purpose of the present study was to investigate lung mycotoxicosis experimentally in mice after an intranasal exposure to spores of S. atra-fungus. One group of mice received one intranasal injection of spores of a toxic strain of S. atra (1 x 10(6) spores) and the other group spores of a less toxic strain. Spores of both strains contained spirolactones and spirolactams while the highly toxic strain contained also trichothecene mycotoxins, satratoxins. The spores containing satratoxins caused severe intra-alveolar, bronchiolar and interstitial inflammation with haemorrhagic exudative processes in the alveolar and bronchiolar lumen. A significant difference was observed in the severity of the lung damage caused by the two strains of S. atra. The spores without satratoxins induced a milder inflammation, so that the toxic compounds of S. atra-spores are most likely responsible for the severity of the lung injury.