Summary Clinical and immunological studies were made in forty‐two patients diagnosed as suffering from hypersensitivity pneumonitis at Osaka Prefectural Habikino Hospital between 1973 and 1977. All the sera from forty‐one patients tested had high litres of antibody against Cryptococcus neoformans in indirect fluorescent antibody tests, and twelve also had precipitins against Cryptococcus neoformans polysaccharide. Only about 10% of control sera from patients with otherlung diseases had low titresof antibody against Cryptococcus neoformans. Antibody against Cryptococcus neoformans was also found frequently in the sera of asymptomatic members of the families of the patients. A possible relationship of Cryptococcus neoformans to hypersensitivity pneumonitis is suggested.

Sixty-six patients, diagnosed as Japanese summer-type hypersensitivity pneumonitis at Osaka Prefectural Habikino hospital between 1973 and 1980, were studied. The diagnosis was based on the clinical features and summer-seasonal nature of the disease. The presence of an aetiological agent within patients" home environment was suggested by the recurrence of acute symptoms of high fever, cough and dyspnoea 5-8 hr after coming home from hospital, and by spontaneous improvement on leaving home, immunological studies revealed the presence of -dnU-Cryptoeoceus antibody in sixty-four of sixty-five patients' sera, by indirect immunofluorescence against Cryptococcus neoformans. Precipitating antibody against culture supernatant protein-antigen of Cr. n<'o/()rmam was detected in more than 80% of sera obtained from patients during the active stage of the disease. The positive result on inhalation provocation-challenge, using culture supernatant protein-antigen, suggested that Cr. neoformans or antigenically related Cryptococcus species may cause Japanese summer-type hypersensitivity pneumonitis. Recent studies reveal that patients with HP have been increasing during the past 10 years in Japan. Hypersensitivity pneumonitis in Japan, including our cases, was

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