Aspergillosis was diagnosed in three of four Peruvian penguins "Spheniscus humboldti" which were brought to the Aquarium of Niagara Falls, N.Y. from Chase Quarantine Station in Florida. The clinical course of the disease was short. Extensive granulomatous pneumonia and air sacculitis was found on the postmortem examination. Aspergillus fumigatus was cultured from the nostrils, lungs and air sac lesions of the three penguins. Being in close contact with the sick penguins, the fourth one was put on prophylactic treatment with Amphotericin B and so far the penguin is alive.