About 10-15% of all couples attempting to conceive will not become pregnant within one year. Among those, the majority will have ovulatory dysfunction, mild male infertility or unexplained infertility. The traditional first line therapy for those couples is ovulation induction or superovulation using clomiphene citrate. Probably due to anti-estrogenic effects of this agent will, some patients will have a thin endometrium as measured by sonography at the time of ovulation. This phenomenon may be associated with a lower chance to conceive. Tamoxifen is a similar molecule that has been used to clomiphene citrate that has been shown to be equally effective to clomiphene in ovulation induction. Preliminary observations showed that tamoxifen does not cause a negative effect on the endometrium as compared with clomiphene, and may increase the chance to conceive in those patients who have a thin endometrium under clomiphene.

Inclusion Criteria:

• Primary or secondary infertility due to:
• Ovulatory dysfunction
• Mild male infertility
• Unexplained infertility
• Endometrium < 6 mm at time of hCG during previous treatment with clomiphene citrate
• Age 18-35

Exclusion Criteria:

• Serious adverse effects under clomiphene citrate or known sensitivity to either tamoxifen or clomiphene citrate