Infertility in women is caused by a variety of hereditary and acquired uterine problems. Ultrasound has been found to be a good, quick, safe, and cost-effective way to assess the size, quantity, and location of abnormalities and to measure endometrial thickness in different phases of menstrual cycle.Objective: The main objective of this study wasto evaluate roleof ultrasound in assessment of endometrial thickness in infertile females of secretory phase. Methods: This is a descriptive study, including eighty two females age 24 to 46 years from University ultrasound clinic, Lahore after the approval of ethical committee of Allied health sciences, University of Lahore. Informed consent was taken before including the subjects in the study. Data was collected according to data collection sheets. Results: The results showed that primary infertility (54.9%) is more in females than secondary infertility (45.1%). There were 10(47.6%) females in primary infertility with 9-12mm endometrial thickness and 11(52.4%) in secondary infertility. 24(57.1%) females in primary infertility with 13-16mm endometrial thickness and 18(42.9%) in secondary infertility. 11(68.8%) females in primary infertility with 17-20mm endometrial thickness and 5(31.3%) in secondary infertility. 3(100%) females in secondary infertility with 21-24mm endometrial thickness.Conclusion: Female patients who initially taking infertility treatment had less endometrial thickness in proliferative phase; their endometrial thickness maybe increased in early secretory phase or at 21st day of their menstrual cycle but they had lost their chance to conceive the pregnancy in proliferative phase due to less endometrial thickness. The females should know the normal endometrial thickness in different phases of their menstrual cycle to conceive the pregnancy.  This study shows ultrasound plays a vital role in detecting endometrial thickness in infertility treatment.