The advent of possible protective therapies for Parkinson's disease has created a need for methods of diagnosing the disease before the clinical features become fully evident. As a number of motor and nonmotor manifestations of the disease emerge months to years before a diagnosis can be made, a battery of clinical tests might be sufficient to identify individuals at an earlier stage than is currently possible using the standard history and physical examination. A list of questions regarding possible risk factors, specific symptoms, and observations of family members could be combined in a self-administered questionnaire that might identify individuals with a high probability of early, but otherwise undiagnosable, Parkinson's disease. Identification of subtle motor features is another possible screening method. For example, handwriting and speech are commonly affected prior to diagnosis; thus, automated analysis of these motor actions might also provide detection of incipient disease.