Crepidiastrum lanceolatum ($H_{OUTT}$) $N_{AKAI}$ (Compositae) is distributed in East Asia including Korea. Genetic diversity and population structure of six C. lanceolatum populations in Korea and two populations in Japan were determined using genetic variation at 19 allozyme loci. The percent of polymorphic loci within the enzymes was 42.1%. Genetic diversity at the species level and at the population level was low (Hes : 0.077; Hep : 0.068, respectively), where-as the extent of the population divergence was relatively low ($G_{ST}$ : 0.093). One of the most striking features of this study was the more significant difference within populations than among populations. An indirect estimate of the number of migrants per generation (Nm : 2.44) indicated that gene flow was moderate among eight populations of the species. In addition, analysis of fixation indices revealed a slight heterozygosity deficiency in some populations and at some loci. Narrow geographic ranges, short-lived perennial herbaceous, and small population sizes are mainly associated with the low level of genetic variation.n.