Infertility is defined as the inability to achieve pregnancy after one year of regular, unprotected intercourse. Evaluation may be initiated sooner in patients who have risk factors for infertility or if the female partner is older than 35 years. Causes of infertility include male factors, ovulatory dysfunction, uterine abnormalities, tubal obstruction, peritoneal factors, or cervical factors. A history and physical examination can help direct the evaluation. Men should undergo evaluation with a semen analysis. Abnormalities of sperm may be treated with gonadotropin therapy, intrauterine insemination, or in vitro fertilization. Ovulation should be documented by serum progesterone level measurement at cycle day 21. Evaluation of the uterus and fallopian tubes can be performed by hysterosalpingography in women with no risk of obstruction. For patients with a history of endometriosis, pelvic infections, or ectopic pregnancy, evaluation with hysteroscopy or laparoscopy is recommended. Women with anovulation may be treated in the primary care setting with clomiphene to induce ovulation. Treatment of tubal obstruction generally requires referral for subspecialty care. Unexplained infertility in women or men may be managed with another year of unprotected intercourse, or may proceed to assisted reproductive technologies, such as intrauterine insemination or in vitro fertilization.