We surveyed by questionnaire 4,673 residents of Izu-Oshima who were 15 or more years of age with regard to Cryptomeria japonica pollinosis. The response rate was 22.3%. In the early spring, nasal symptoms were reported by 8.9% of the respondents, ocular symptoms by 5.7%, and dermal symptoms by 8.1%. On scratch tests of symptomatic subjects, 13.8% were positive for Cryptomeria japonica antigen, and 33.3% had an IgE RAST score of 2 or more. The peak Cryptomeria japonica pollen concentrations between February and April 1990 were 118/cm2 on March 7 at the Northern Clinic and 271/cm2 at the Southern Clinic. A second questionnaire survey (response rate: 53.1%), designed to estimate the number of persons with Cryptomeria japonica pollinosis among all residents, revealed that 4.7% concurrently had three or more nasal symptoms and two ocular symptoms. By combining these results with those of a telephone survey of 100 randomly selected nonrespondents, 5.64% of all inhabitants were estimated to have suspected Cryptomeria japonica pollinosis.