Immature fruits of Japanese pear, Pyrus serotina, were picked and homogenized with 70% ethanol. The homogenate was extracted with 70% ethanol three times and filtrated. The filtrate was concentrated, the residue adjusted to pH 8.4 with 1N NaOH and then extracted with n-butanol. The butanol phase was evaporated and aqueous extract of the residue was added to a Dowex-50(H⁺ form) column and eluted with water, 1N NH₄OH and 5N NH₄OH successively. Cytokinin activities in the three fractions were tested by tobacco(Wisconsin No. 38) pith callus assay. Cytokinin activities were detected in both 1N and 5N NH₄OH fractions, but not in the water. Based on these results, the NH₄OH fractions (Am-fraction) were combined and analysed by microcrystalline cellulose thin layer and gas liquid chromatographies. The fraction separated by TLC for the bioassay of cytokinin revealed activities at Rf values 0.5 and 0.7. Analyses of TMS derivative of Am-fraction by GLC gave four peaks. Mixture of the TMS derivative with that of authentic zeatin analyzed on GLC revealed that peak 2 coincides with zeatin, and peak 1 was considered to be dihydrozeatin.