Numerous drugs and medications have been shown to have adverse effects on male fertility, acting through diverse mechanisms. These drugs are summarized in Table 2. Mechanisms of impaired fertility include direct effects on germ cells or their supporting cells, effects on the delicately balanced HPG axis, effects on erectile or ejaculatory function, and effects on libido. In a thorough fertility evaluation of the male partner, the physician should determine what medication the patient is taking and his social habits involving alcohol consumption, tobacco, and recreational drug use. Most adverse effects from drugs and medications can be reversed by simply discontinuing the offending agents; however, in some instances, such as chemotherapeutic regimens, the medications cannot be discontinued, and pretreatment sperm cryopreservation remains critical. It is essential for urologists treating infertile men to be familiar with the more commonly encountered drugs and medications that may affect the potential for fertility.