OBJECTIVES: Focusing on critically ill children with cardiac disease, we will review common causes of fluid perturbations, clinical recognition, and strategies to minimize and treat fluid-related complications. DATA SOURCE: MEDLINE and PubMed. CONCLUSIONS: Meticulous fluid management is vital in critically ill children with cardiac disease. Fluid therapy is important to maintain adequate blood volume and perfusion pressure in order to support cardiac output, tissue perfusion, and oxygen delivery. However, fluid overload and acute kidney injury are common and are associated with increased morbidity and mortality. Understanding the etiologies for disturbances in volume status and the pathophysiology surrounding those conditions is crucial for providing optimal care.