In a randomized, single-blind, crossover study, we evaluated physical disability in moderately advanced Parkinson's disease (PD) patients after 4 weeks of normal physical activity and 4 weeks of an intensive physical rehabilitation program. We used a timed motor task and a standard assessment of PD severity (the Unified Parkinson's Disease Rating Scale [UPDRS] with subscales for mentation, activities of daily living [ADL], and motor function) completed by an investigator blinded to the physical rehabilitation status of the patient. Following physical rehabilitation, there was significant improvement in the UPDRS ADL and motor scores, but no change in mentation score. During the 6 months following physical rehabilitation, patients did not regularly exercise, and the UPDRS scores returned to baseline. We conclude that physical disability in moderately advanced PD objectively improves with a regular physical rehabilitation program, but this improvement is not sustained when normal activity is resumed.