A 58-year-old man, a carpenter, had been suffering from cough, rhinorrhea, wheezing, dyspnea and ocular itching a few minutes after each exposure to the sawdust of "Ayous" wood (Obeche, Triplochiton scleroxylon) since starting to work on this imported wood in 1998. Although his symptoms improved soon after exposure, he had a secondary response several hours later. He had no symptoms when working with any other woods. In January, 2001, he came to our hospital, and occupational asthma was suspected. Peak flow monitoring revealed immediate- and late-type responses when he was exposed to Ayous wood dust. Non-specific bronchial hyperresponsiveness to acetylcholine was positive. An immediate skin test with Ayous wood extract was positive. In the RAST inhibition test, his serum revealed specific IgE antibody to Ayous extract. Bronchoprovocation with Ayous wood extract demonstrated immediate and later type responses (dual response). Occupational asthma caused by Ayous wood dust was confirmed. This is the first case report of occupational asthma caused by Ayous wood in Japan.