Exercise is often noted as an important component in a comprehensive approach to the management of Parkinson disease (PD). Most studies of exercise have examined the effects of short-term interventions and have tested participants on their anti-Parkinson medications. As such, these studies have not been able to determine whether or not exercise may have a disease-modifying effect in people with PD. The investigators recent work has shown the potential benefits of dance as a form of exercise for individuals with PD, but, like previous work, has only examined short-term interventions. The investigators think that dance may be ideally suited for study over a longer period of time because dance incorporates many of the features recommended for inclusion in PD-specific exercise programs in a format that is known to be engaging and to enhance motivation to participate in healthful behaviors. As such, the investigators aim to determine both the short- and long-term effectiveness of a community-based dance program for individuals with Parkinson disease and to determine how physical function changes over time in individuals with PD who do not exercise as compared to those who exercise regularly. The investigators hypothesize that: