Abstract: In order to evaluate drought stress on relative water content (RWC) and chlorophyll content of 27 Sesame genotypes, a factorial experiment based on randomized complete block design with three replications was conducted in 2006 in Moghan region, Iran. Factors were 27 Sesame genotypes (Karaj 1, Yekta, Oltan, Moghan 17, Naz takshakheh, Naz chandshakheh, Borazjan 2, Borazjan 5, Darab 14, Varamin 37, Varamin 237, Varamin 2822, Zoodrass IS, Hendi, Chini, Yellow white, 5089, Panama, Do-1, TF-3 , TKG-21, J-I, RT-54, Hendi 9, Hendi 12, Hendi 14 and Jiroft) and irrigation levels (full irrigation and irrigation until flowering stage). Results showed that Varamin 2822 and Varamin 237 genotypes had the highest RWC of 84.100 and 81.217%, respectively. The most chlorophyll a content was observed in Hendi 9 genotype of 106.237, the most chlorophyll b in Karaj 1 genotype of 84.665 and the most chlorophyll total in Hendi genotype of 182.395 mg g-1 leaf fresh weight. It seems that Varamin 2822 genotype having the highest RWC and Hendi 9 and Hendi genotypes having the most chlorophyll a and chlorophyll total, respectively, are recommended for planting in arid and semi-arid conditions.