Infertility is a significant medical problem that affects many couples. Evaluation is the starting point for treatment of infertility as it may suggest specific causes and appropriate treatment modalities. Although the history and physical examination provide important information, specific diagnostic tests are required to evaluate infertility. Because the causes of infertility can be multifactorial, a systematic approach typically is used and involves testing for male factor, ovulatory factor, uterotubal factor, and peritoneal factor. Many of these diagnostic tests are laboratory based, including semen analysis, serum progesterone level, serum basal follicle-stimulating hormone level, and clomiphene citrate challenge, and can be done by the primary care physician. Moreover, by understanding the infertility evaluation, the primary care physician can serve as an important resource for advice about infertility. This article briefly reviews the diagnostic approach to infertility, with particular emphasis on important laboratory tests used for evaluation.