The intravenous administration of fluids is one of the most important aspects of patient care in hospitalized animals. Intravenous fluids are administered to replace or prevent dehydration, treat hypovolemic shock and intravascular volume depletion, correct acid-base and electrolyte abnormalities, and maintain vascular access for administration of drugs, blood product components, and parenteral nutrition. Intravenous catheterization also can provide a means of blood sample collection, thus avoiding frequent and uncomfortable venipunctures in critically ill animals. Although the benefits of intravenous catheterization and fluid administration are numerous, inherent risks are associated with the procedures, and care must be taken to avoid potential complications.