Genetic diversity assessment of genetic resources maintained at Gene-Banks has importantrnimplication for future improvement, conservation and collection activities. However, suchrninformation is not available for sesame collected by IBC, Ethiopia. Intersimple sequence repeatrn(ISSR) marker was used to assess the level of geneticdiversity, genetic structure and geneticrndistance, and to indirectly estimate the level of gene flowamong populationsof sesame inrnEthiopia.A total of 120 (82 Ethiopian and 38 exotic) sesame accessions and six ISSR primers,rnfive of which were dinucleotides (810, 818, 834, 844, 860) and one pentanucleotides (880)rnprimers were used. DNA was extracted using a triple CTAB extraction method from silica gelrndried bulked sample of five randomly selected individual plants per accession at the stage ofrnthree to four weeks after planting. A total of 58 clear and reproducible bands were amplified, outrnof which 44(75.86%) were observed to be polymorphic. The number of polymorphic loci rangedrnfrom four for primer-834 to eight for the other primers.Comparative assessment of Ethiopianrnaccessions (considering as a single large population) verses exotic accessions indicated thernpresence of higher polymorphism among accessions collected from Ethiopia (75.85)than thernexotic accessions (65.52). Primers 810, 818 and 860 showed the highest percent polymorphismrn(88.89%) and the least polymorphic bandswere scored by primer 834 which is only 40.00 %.rnGrouping Ethiopian accessions into administrative region-based populations and the exoticrnaccessions in to country based populations showed samples from Welega were the mostrndiverse,with gene diversity value of (0.26) followed by samples from Tigray (0.20) and Shewarn(0.20). Samples from Gojam (0.10) and Sudan (0.12) were the least diverse. The average generndiversity relative to the overall population was 0.24 considering accession from differentrnadministrative region of Ethiopia and exotic accessions as independent population. AMOVArnwithout grouping revealed that higher percentage of variation (94.09%) is attributed to thernwithin population variation while the remaining variation is due to the among populationrnvariation (5.90%). Inter-population genetic distance (D) ranged from 0.031 to 0.165 for thernoverall population. Among the pairwise population comparisons made within Ethiopianrnpopulations,accessions from Welega and Harerge showed the highest genetic distance (0.16)rnand accessions from Shewa and Harerge show the least genetic distance (0.041). From thernexotic accession,samples of South East Asia are distantly related to most of the Ethiopianrnaccessions. Genetic distance between the other pairwise combinations of populations was veryrnlow, with the least genetic distance being between samples of Mexico and Tanzaniarn(0.031).UPGMA analysis of Ethiopian sesame populations revealed two major groups and threernoutliers (Cultivated, Welega and Illubabore). The first major cluster again forked into two subrngroups the first containing Tigray, Harerge and Shewa populations, while the second containedrnGamo Goffa, and Wello populations. The second major cluster comprise of accessions fromrnnorth western part of Ethiopia mainly from Gojam, Benishangul Gumuz and Gonder.In the 3Drnplot, with the exception of few accessions that come from Welega, Wello and Ilubabore, most ofrnthe individual accessions that represent different populations spread all over the 3D space.rnKey words:Ethiopia, genetic diversity, ISSR, Sesame (Sesamum indicum L.)