This chapter focused on a variety of infections caused by bacteria, viruses, fungi, and parasites. A brief review of the immune system was provided to explain the basic forms of defense the body uses to prevent infections as well as what happens when these defenses fail. Pharmacotherapy was reviewed, covering the most common antibiotics, antifungals, antivirals, and medications used to treat infections, including COVID-19, HIV, STIs, TB, and protozoal and helminthic infections. Mechanisms for the development of anti-infective resistance were discussed, including the fact that health care professionals must always be mindful of how they use anti-infectives to ensure their continued effectiveness in the future. The importance of client adherence was stressed, not only so the client can get the best treatment possible but also to help curb resistance. Given that some conditions are often associated with negative stigmas, nurses must strive to foster open and nonjudgmental environments in which clients from all backgrounds can feel comfortable getting the health care they deserve.