Background: Ovulation induction remains a milestone in the treatment of women with anovulatory infertility. For the last 40 years, the first line of treatment for anovulation in infertile women was clomiphene citrate (CC). It was appropriate because the drug was highly effective in inducing ovulation in selected patients with the advantages of being orally administered, relatively safe, and inexpensive. Letrozole (AI) has been introduced as a new treatment option that could challenge CC for ovulation induction. AIs are a new group of drugs join the fertility treatments. They are orally administered, easy to use and less expensive than other measurements like gonadotrophines, but more expensive than CC, and with minor side effects. Tamoxifen (TMX) has been also introduced as a simple oral alternative to CC in ovulation induction. It is similar in structure to CC, but with no peripheral anti-estrogenic actions, so, has no adverse effects on endometrial thickness and cervical mucus. Objective: To compare the effect of clomiphene citrate, letrozole and tamoxifen on the endometrium in anovulatory patients using endometrial thickness and spiral artery Doppler as parameters for comparison during ovulation induction cycle. Patients and methods: The study was carried out in EntagEl-HarbyHospital. The patients were recruited from the outpatient infertility clinic between January 2021 and July 2021. This prospective study included 300 infertile women who were diagnosed as anovulatory infertility and meet the inclusion criteria. Patients were divided into three equal groups giving in Group 1: Clomiphene citrate, Group 2: Letrozole, and Group 3: Tamoxifen. Results: There was no statistically significant difference in the patients' characteristics (age and BMI) between the three studied groups. There was a statistically significant difference as regards duration of infertility in the three studied groups. Enometrial thickness was better under letrozole and tamoxifen therapy. Spiral artery Doppler showed lower impedance with a lower resistance index (RI) and pulsatility index (PI) under letrozole and tamoxifen therapy. Ovulation rate was not significantly different between the three drugs. Pregnancy rate was not significantly different between the three drugs. Conclusion: Letrozole and tamoxifen can induce similar or even better results than clomiphene citrate, and each of them can be used as a first line option for treatment of anovulatory infertility.