A 22-year-old woman developed recurrent episodes of fever, cough and dyspnea after repeated exposure to a misting fountain at home. A diagnosis of extrinsic allergic alveolitis (EAA) was made by detection of serum antibodies against the fountain water, by culture of Bacillus subtilis, Mucor racemosus, Mucor mucedo, and Saccharomyces cerevisiae from the water, and by detection of specific IgG antibodies against Bacillus subtilis and the Mucores. The diagnosis was confirmed by a restrictive lung function pattern, and a highly increased total cell count with a lymphocytosis of 39 % in the bronchoalveolar lavage. An inhalation challenge with the misting fountain resulted in a positive reaction. Because this humidifier system has recently become widespread at home, clinicians should be aware of this specific type of EAA which may be called "misting fountain alveolitis".