This chapter provides information for qualified veterinary nurses on how to establish and run a critical care unit or area within a practice. Committed and diligent nursing plays an essential part in the successful treatment of critically ill patients. This can best be provided in an area dedicated for the higher level of care required for the critically ill. Critical care is a unique speciality that involves treatment of patients with both medical and surgical diseases. A factor common to all critical patients is the potential to develop problems that can be rapidly life-threatening. The aim of the critical care unit is to facilitate early recognition of these problems. The chapter discusses What is a critical care unit; Organization of the critical care unit; Patient care; and Infection control.