Postural instability is one of the most disabling features of Parkinson's disease. Many factors contribute to balance impairment of Parkinson patients, including disturbed postural reflexes and poor control of voluntary movement. Additional factors which place Parkinson patients at risk for falls are side-effects of medication (dyskinesias), the poor response of postural instability to antiparkinsonian medication, orthostatic hypotension, gait abnormalities, muscular weakness in leg muscles and superimposed age-related changes such as reduced peripheral sensation. Future studies should not only investigate means of preventing falls in unstable patients, but should also be directed towards development of new treatment. Because accumulating evidence indicates that postural instability is at least partially related to non-dopaminergic lesions, these novel therapeutic approaches should be aimed at overcoming non-dopaminergic neurotransmitter deficiencies.