Abstract: A karyotype analysis for Sophora flavescens Ait. (Legumino-sae) has been carried out and the number of chromosomes has been found to be 2n=18, in accord with those reported by Kawakami^[3], Hexob^[8] and Kodama^[4], but disagreeing with the report of 2n=28 of Nagl^[6]. According to the chromosomal terminology defined by Levan and al.^[5], the karyotype for-mula is K(2n)=18=2M(SAT)+10m+4m(SAT)+2sm. In the light of Stebbins'^[7]classification of karyotypic asymmetry, the ka-ryotype belongs to "2A" type and should therefore be considered as a rather primitive one. Aneuploidy is evident in the ancient and diverse genus Sophora L. The genus has a wide range of chromosome num-bers with n=14, 11, 9 and 8, with the most frequent number n=9. It is generally admitted that x=14 is most likely thebasic number for Tribe Sophoreae as a whole, and the number has been originated from polyploid caesalpinioid stock. Sub-sequent evolution has involved descending aneuploidy probably due to framentation as proposed by Yakovlev and others^[2].The only species:Sophora japonica, S. affinis and S. chinensis (probably identical with S. japonica as suggested by P. C.Tsoong and al.^[1]) heretofore known with n=14 in the genus Sophora are all arborescent, while species with lower numbers (n=11, 9 and 8) are usually smaller trees or shrubs or even perennial herbs. It seems that the perennials S. flavescens and S. alopecuroides L. as well must be viewed cytologically as de-rived aneuploids from members having a higher basic number in the genus.