Compliance, reliability, and validity of self-monitoring for physical disturbances of Parkinson's disease. The Parkinson's Symptom Diary. Previous clinical research in Parkinson's disease has recognized the value of self-monitoring procedures in which patients observe and record the frequency and severity of their own symptoms as these occur within the patient's social and work environment. We discuss issues of methodology and report a study of compliance, test-retest reliability, and validity with a new self-monitoring instrument, the Parkinson's Symptom Diary. Two recordings of frequency (loss of balance, hesitation-freezing) and two ratings of severity (tremor, difficulty walking) were made four times daily for one week by patients (N = 73) who were without apparent loss of cognitive or memory functions. A total of 91% of the diaries received (97% of requested) met strict compliance criteria so that independent sampling over days could be assumed. Test-retest stability over one month was demonstrated for each score (all Spearman rho greater than .85) in a representative subsample of 28 patients. Criterion validity was demonstrated for each score by an expected pattern of correlations with independently obtained observer ratings of the same or related indices of disease, and by comparison with Hoehn and Yahr disability stages. By its simplicity, this self-assessment device can be an invaluable complement to traditional methods of clinical and laboratory assessment in the care and evaluation of Parkinson patients. 