The risks attendant on regional anaesthesia derive from the condition of the patient, the technique employed and the skill, or lack of skill, on the part of the anaesthetist. Patient-determined risk factors are: existent diseases and pathological conditions which in many cases cannot be rectified pre-operatively. The main difficulties and complications of regional anaesthesia arise from mechanical, pharmacodynamic and toxic factors and infection. Each technique carries its own specific risk. With due care many of the complications can be prevented.