This chapter discusses patient-controlled analgesia (PCA). Patient-controlled analgesia (PCA) is a mainstay in the spectrum of pain management for acute postsurgical pain. Optimal perioperative analgesia is best achieved with a multimodal approach that includes oral medications, intravenous (IV) PCA and regional anesthesia. When used properly, it is theorized that IV PCA provides effective analgesia due to maintenance of the serum minimum effective analgesic concentration (MEAC). The advantages of IV PCA use include better pain control compared to non-PCA and increased patient satisfaction due to less administrative delays compared to intramuscular (IM) or IV administration. Unauthorized activation of PCA therapy by a third party can bypass the safety advantage of PCA. Description of PCA and parameters, and choice of opioid and dosing paradigms are also discussed in this chapter.