The genus Polygonatum (Liliaceae-Polygonateae or Convallariaceae-Polygonateae) includes ca. 58 species and is widely distributed in the northern hemisphere, from the subtropical to subarctic zone (Bentham and Hooker 1883, Krause 1930, Hutchinson 1934, Dahlgren et al. 1985). According to Tang (1978), the species referred to three series, i. e., Ser. Bracteata, Ser. Alternifolia and Ser. Alte-lobata, occur in Japan, Taiwan and Cheju Island, Korea. The plants of Ser. Bracteata are distributed in northern and northeastern China, Far Eastern U. S. S. R., Korea and Japan, and include 6 species and 2 varieties, among which 5 species and 2 varieties occur in Japan and Cheju Isl. Among the species belonging to this series, chromosome numbers and karyotypes of P. desoulavyi var. desoulavyi and P. involucratum from China, U. S. S. R. and the Korean Peninsula have been reported (Sokolovskaya 1966, Lee 1967, Abramova 1971, Kim and Kim 1979, Wang et al. 1987), but no reports have been made for the plants in Japan and Cheju Isl. The remaining species of this series are so far unknown karyologically (cf. Table 1). Ser. Alternifolia, which comprises ca. 35 species, is the largest group of the genus, and is distributed in Europe, Asia and North America, among which 8 species, 6 varieties and 1 form occur in Japan, Taiwan and Cheju Isl. Detailed karyotype analyses have been made on the North American as well as European taxa belonging to this series by various authors (Eigsti 1942, Suomalainen 1947, Therman 1950, Kawano and Iltis 1963b, Nowakowska and Zeglicka 1972, for others see Table 1). However, only scattered information has been available for the plants from northeastern Asia. The Bracteata group and the Alternifolia group have been studied taxonomically by Franchet and Savatier (1878), Komarov (1935), Satake (1942), Abramova (1975) and Tang (1978). However, taxonomic concepts of these two groups by the above authors (l. c.) are different, especially as to the identity of P. inflatum. Abramova (1975) used chromosome numbers and karyotypes for the delimitation of these groups in addition to gross morphology. But, her results on chromosome numbers and karyotypes for the Japanese species are different from those of the other authors (cf. Table 1). The purpose of the present study first, is to report the detailed chromosome morphology of all the species belonging to Ser. Bracteata and Ser. Alternifolia occurring in Japan and its adjacent regions through a critical examination of many individuals from different localities, and second, to revise taxonomically these two series based on the results obtained. © 1990, Japan Mendel Society, International Society of Cytology. All rights reserved.