Patient-controlled analgesia (PCA) provides improved titration of analgesic drugs, thereby minimizing individual pharmacokinetic and pharmacodynamic differences. Patient-controlled analgesia decreases patient anxiety resulting from delays in receiving pain-relieving medication and from the slow onset of analgesic action when these drugs are administered either intramuscularly or in the extradural space. With PCA therapy, patients are reportedly able to maintain a near optimal state of analgesia with minimal sedation and few side effects. The potential for overdose can be minimized if small bolus doses are used with a mandatory lockout interval between successive doses. Finally, studies of the cost-effectiveness of PCA therapy are important if this therapeutic approach is to achieve more widespread acceptance.