To evaluate drought tolerance in cultivated ( Carthamus tinctorius L.) and wild safflower ( C. oxacantha Bieb) populations, an experiment was conducted at research farm of College of Agriculture, Isfahan University of Technology located at Lavark-Nafafabad in 2008. A randomized completed block design with 3 replications was used in each of three environmental conditions of irrigation after 80, 130 and 180 mm evaporation from pan, respectively. Evaluation of morphological traits and results of variance analysis revealed a significant difference among genotypes for all studies traits. There was a considerable variation for number of heads per plant and wild safflower had significantly higher value for this trait. Moisture stress also had a significant effect on all studied traits. Clear differences existed between the two species (cultivated and wild) for moisture stress tolerance with the wild species being more tolerant than the cultivated one. Increasing water stress level caused significant reduction in the seed yield of cultivated genotypes whereas the wild genotypes were not affected as much. Correlation coefficient for cultivated safflower showed that number of seed per head, days to flowering, head weight and plant height had a positive correlation with seed yield. Similarly number of heads per plant, plant height and seed weight per head had positive correlation with seed yield in wild safflowers. Factor analysis revealed four factors in cultivated genotypes under non-stress condition and three factors at intense moisture stress level which justified 90 and 75 percent of the total variation respectively. Also factor analysis of wild species showed that the first there factors, justified more than 80 percent of total variation at both moisture stress levels. Results of cluster analysis showed that all studied genotypes were clustered in 3 groups which wild genotypes were grouped in the same cluster. Results indicated that the Stress Tolerance Index (STI) is an effective selection criterion for identification and introduction of tolerant genotypes. Based on this index among cultivated genotypes, Koseh at mild drought stress level and Kashan at intense stress level were the most tolerant accessions. Similarly among wild genotypes, Azary at mild Key words: cultivated safflower, wild safflower, drought stress, STI index, biplot analysis
