In recent years, biological approaches such as mycorrhizal symbiosis have been used to alleviate the detrimental effects of drought stress. In a pot experiment the responses of three leek genotypes including Carantan 2 and two Iranian leek genotypes to drought stress and mycorrhizal colonization were compared at Ramin University of Agriculture and Natural Resources in 2010. The experiment was conducted in a completely randomized design consisting of a 3×3×2 factorial combination of three soil moisture levels (the pots were watered when 40, 60 and 80 percent of available water was consumed), two mycorrhizal status (with and without mycorrhiza) and three leek genotypes (Shdegan, Esfahan and Carantan 2). The treatments were replicated four times. The results showed that drought stress significantly decreased all growth parameters including plant height, root and leaf dry weights and total root length. However, mycorrhizal colonization increased all of these parameters at all drought stress levels. Drought stress significantly decreased root length colonized and the percentage of root colonization. Despite this decline in mycorrhizal growth, the response of three leek genotypes increased as drought stress was increased. Among leek genotypes, Shadegan genotype with short root length and low proliferation had the greatest mycorrhizal growth response compared with the two others genotypes. Leaf proline accumulation increased by increasing drought stress. However, this accumulation was lower for mycorrhizal leek genotypes which could be due to the alleviation of the effect of drought stress by mycohhizal fungus. The results of this study indicated that Shdegan genotype with a weak root system had the greatest mycorrhizal dependency.