We have analyzed 11 Y-STR loci (DYS19, the two DYS385 loci, DYS388, DYS389I/II, DYS390, DYS391, DYS392, DYS393, DXYS156Y) in 700 males from ten ethnic groups in east Asia in order to evaluate their usefulness for forensic and population genetic studies. A total of 644 different haplotypes were identified, among which 603 (86.14%) were individual-specific. The haplotype diversity averaged over all populations was 0.9997; using only the nine Y-STRs comprising the "minimal haplotype" (excluding DYS388 and DXYS156Y) it was 0.9996, a value similar to that found in 1924 samples from other Asian populations (0.9996; Lessig et al. Legal Medicine 5(2003) 160-163), and slightly higher than in European populations (0.9976; n=11,610; Roewer et al. For Sci International (2001) 118:103-111). All of the individual east Asian populations examined here had high haplotype diversity (> or =0.997), except for the Mongolians (0.992) and Manchurians (0.960). The most frequent haplotype identified by the nine markers was present at only 1% (7/700). Population comparisons based on Phi(ST) or rho genetic distance measures revealed clustering according to the traditional northeast-southeast distinction, but with exceptions. For example, the Yunnan population from southern China lay among the northern populations, possibly reflecting recent migration, while the Korean population, traditionally considered northern, lay at the boundary between northern and southern populations. An admixture estimate suggested 55(51-59)% northern, 45(41-49)% southern contribution to the Koreans, illustrating the complexity of the genetic history of this region.