We have been developed super-sensitive method of Cry j 1 measurement by ESR radical immunoassay using p-acetamidophenol and hydroxylamine system. The detection limit for Cry j 1 was 3.5 pg/ml. It is reported that the average content of Cry j 1 in each Cryptomeria japonica pollen is about 6 pg, therefore, we can detect one grain or even less one grain of the pollen by our method. It was possible to inform the useful information for sensitive C. japonica pollinosis patients before development their symptoms due to the super-sensitive measurement.