Tremor, a rhythmical involuntary oscillatory movement, is the most common movement disorder to afflict man. It is classified on both phenomenonological and aetiological grounds and can be measured using clinical rating scales or physiological techniques. Investigation of tremor is guided by the clinical scenario but where appropriate may include neurophysiological tests, imaging the nigro-striatal dopaminergic system with SPECT or PET, cerebral MR imaging and also genetic testing. Treatment of tremor depends on the severity and cause of tremor and includes medical therapy and stereotactic surgery including deep brain stimulation.