 The purpose of this protocol is to compare the impact of fesoterodine to placebo on urinary urgency and nocturnal sleep problems in a heterogeneous population of PD patients in a cross-over fashion. Although OAB can be effectively treated, there is compelling and scientifically sound methodological reasons for its use as participants in the study will not face additional risks of serious or irreversible harm from exposure to placebo. Placebo controlled trials are the most rigorous test of treatment efficacy for evaluating a medical therapy and will require fewer subjects than active control trials. Lastly, anticholinergic studies have shown to have a very large placebo effect and are only partially effective in treating voiding symptoms, which justifies the use of a placebo arm. 