Objectives: To evaluate the role of sildenafil (Viagra) in improving the endometrial thickness and implantation rate in patients undergoing lUl having thin endometrium. Methods: The present study, a randomized control trial, was conducted in Department of Obstetrics and Gynaecology in collaboration with Department of Radiodiagnosis for a period of six months. Patients registered in infertility clinics with thin endometrium in previous cycles (<9 mm) having ovulation with clomiphene citrate but failed conception were randomly allocated into 25 cases and 25. controls. Cases received 25 mg vaginal suppositories of sildenafil four times a day and controls received no treatment.