We encountered a family in which two of four members, the husband and his wife, had summer-type hypersensitivity pneumonitis at the same time, about two months after they moved to the residence. A 45-year-old man had cough, fever and exertional dyspnea. Chest computed tomography showed diffuse centriloblar ground-glass attenuation in both lung fields. His 43-year-old wife had chest small nodular shadows and similar symptoms to his husband. Serum anti-Tricosporon cutaneum (T. asahi: serotype II and T. mucoides: serotype I) antibodies of both patients were at the positive level. They were given diagnosis as summer-type hypersensitivity pneumonitis by radiological, serological and histological examinations. The symptoms in both cases were improved immediately after administration of systemic corticosteroid. Summer-type hypersensitivity pneumonitis was assumed to be caused for about two months duration of expousure to antigen.