Drought leaves adverse impacts on crop plants, including oilseed plants. This research was aimed at studying growth, chlorophyll fluorescence, proline, yield and yield components of sesame genotypes under different moisture regimes. A 4-replicate split plot RCBD field experiment was conducted at the Lavark Research Farm, College of Agriculture , Isfahan University of Technology, Isfahan-Iran, in 2007. Three levels of irrigation consisting I 1 as control= irrigation after 75 mm evaporation from the standard irrigation after 110 mm evaporation from the standard irrigation after 145 mm evaporation from the standard Class A Pan servred as main plots. Four sesame genotypes consisting Non branching Naz, Yekta, Varamin and Oltan were considered as sub plots. Chlorophyll fluorescence parameters (F0, Fm and Fv/Fm), proline and chlorophyll content of leaves, Leaf Area Index (LAI) at capsule formation stage, capsules/plant, grains/capsule, grain yield, oil percent and yield, biological yield and harvest index were measured. LAI was negatively affected by drought, leading to an average of 1.1 at I 3 , compared to 2.46 at I 1. Irrigation regimes differed in terms of Fm at grain filling stage. Drought increased leaf proline content by 59%. Grain yield at I 3 (625.1 kg ha -1 ) was 48% lower than that at I 1 (1211.9 kg ha -1 ), due apparently to the greater capsule/plant (42%) and grain/capsule (37%) at the former irrigation level. The highest (584 kg ha -1 ) and lowest (482.2 kg ha -1 ) oil yields were observed with Yekta and Oltan, respectively. Irrigation regime left significant effect on biological yield, with I 1 (6390.9 kg ha -1 ) outyielding I 3 (3248 kg ha -1 ). It could be concluded that, drought affects sesame growth and grain yield significantly and this negative effect is through the photosynthetic surfaces, rather than the quantum efficiency of photosystem II. Furthermore, leaf proline content variations under different moisture regimes does not neccessarily indicate sesame , s resistance to drought.