OBJECTIVE: To assess the predictive value of baseline measures of impairment, disability, and quality of life for the timing of initiation of symptomatic treatment in early Parkinson disease (PD). DESIGN: Inception cohort analysis. SETTING: Ambulatory population from multiple sites in the United States and Canada. PARTICIPANTS: Four hundred thirteen patients with early, untreated PD who participated in 2 double-blind trials that assessed the potential of experimental drugs to serve as disease-modifying agents in PD. Intervention Participants were randomized into treatment groups: creatine (n = 67), minocycline (n = 66), coenzyme Q10 (n = 71), GPI-1485 (n = 71), and placebo (n = 138). Main Outcome Measure Time between baseline assessment and need for the initiation of symptomatic treatment for PD. The following baseline variables were assessed for their relation to the main outcome measure, while adjusting for possible treatment effect: sex; age; level of education; race/ethnicity; disease duration; occupational status; and Unified Parkinson Disease Rating Scale (UPDRS), Medical Outcomes Study Short Form Survey, Modified Rankin Scale, Schwab and England Activities of Daily Living Scale, Total Functional Capacity Scale, 39-item Parkinson Disease Questionnaire, and Geriatric Depression Scale scores. Variables reaching statistical threshold in univariate analyses (alpha = .15) were entered into a multivariable Cox proportional hazards regression model using time to symptomatic treatment as the dependent variable. RESULTS: Approximately half (48.5%) of the participants reached end point within 12 months. Higher baseline impairment and disability, as determined by UPDRS III (motor section), UPDRS II (activities of daily living section, participant rating), and Modified Rankin Scale scores and level of education were independently associated with an earlier need for symptomatic treatment. CONCLUSIONS: In early PD, greater impairment and disability and higher level of education are independently associated with an earlier need for symptomatic treatment.