To determine mean change in visual acuity, corneal astigmatism and clinical appearance of pterygium after intralesional injection of 5-Fluorouracil.This was a Quasi experimental study conducted at Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan from June 2014 to May 2015. Total 68 eyes of 54 patients were included in the study. Patients were treated by injecting 0.1 ml of 5-FU (5mg) weekly injections for 04 weeks. All the patients underwent ophthalmic clinical examination that included Uncorrected distant visual acuity (UCVA), corrected distant visual acuity (CDVA), keratometery with Auto Ref-keratometer (RK-F1, Canon) and slit lamp examination before and 04 weeks after the last injection.Total 68 eyes of 54 patients (18 females and 36 males) were treated with intralesional injection of 5 FU. Out of total, 30 were right eyes while 38 were left eyes. Age of patients ranged from 23 to 53 years with mean age of 39.2 ± 4.90 years. Mean UCVA and corneal astigmatism before treatment were 0.162 ± 0.167 and 2.12 ± 1.53 respectively while the same parameters 04 weeks after last injection of 5 FU were 0.166 ± 0.168 and 1.92±1.45 respectively. The magnitude of induced change in astigmatism was (0.235 ± 1.35). Ninety seven percent of the patients showed improvement in clinical appearance.Intralesional 5-FU injection results in significant clinical and cosmetic improvement of primary pterygium.