A precise high-throughput approach was used to characterize diversity in 28 Eritrean sorghum landraces, and to compare this diversity to representative samples of the world sorghum collection. Pools of simple sequence repeat (SSR) markers were sized and scored on automated DNA-sizing gels. An exceptionally high level of diversity was observed among the 28 Eritrean landraces, compared to other sorghum germplasms, in both the number and size range of SSR alleles. Individual landraces were found to carry a high level of within-population diversity and heterozygosity, and between-population diversity was equally high. Eritrean sorghums could be clustered into 7-10 major subgroups, with most (but not all) classifications agreeing with descriptions by farmers. Clustering did not concur particularly well with the major classification system applied in Eritrea, highland versus lowland. Eight of the Eritrean landraces grouped with other sorghums in the world collection, particularly those from Ethiopia/Sudan and India or of the durra and caudatum races, but most Eritrean sorghums clustered in a separate subgroup. These results indicate that a great deal of germplasm diversity and genetic novelty are available in Eritrean sorghums, and that SSR markers can contribute to the wise use of this diversity for sorghum study and improvement.