Pterygium considered as a common inflammatory and proliferative growth that extends across the limbus and can invade the cornea. It had been found that a long standing Pterygium can be associated with the changes in corneal endothelial layer.Subjects and method: In our study an eighty-one patients (162 eyes) with unilateral pterygium were randomly taken and consecutively enrolled at the out-patient clinic in Ibn Al-Hiatham Eye Teaching Hospital, using specular microscope, the endothelial density, hexagonality and coefficient of variation in cell area were measured for both eyes, using the results of normal eyes for comparison.Results: This study showed a significant decrease in means of endothelial cell density and % of hexagonal cells in affected eyes versus healthy eyes (P0.05), mean of endothelial cell density 2385.8 ± 220.74 versus 2487.9 ± 208.2 ( P-value= 0.003 ) , mean of % of hexagonality 46.92 ± 9.16 versus 53.30 ± 8.64 ( P < 0.001). The study showed no significant difference in coefficient of variation of affected eyes versus healthy eyes, 34.86 ± 5.06 versus 35.15 ± 5.50 (P =0.174).There were significant differences between means of coefficient of variation by size of pterygium. Type I 32.34 ± 3.32, Type II 34.09 ± 4.58, type III 38.47 ± 5.65 (P0.002). There was significant negative linear correlation between endothelial cell density and duration of pterygium among affected eyes.