In a case-control study involving 400 study subjects, we found a higher prevalence of restless legs syndrome (RLS) in our Parkinson's disease (PD) patients compared to controls (3.0% vs 0.5%) (odds ratio 6.2) (p=0.07). Polysomnographic studies confirmed that study subjects with RLS had grossly elevated PLMS index, PLMS arousal index and reduced sleep efficiency. None of these PD patients reported a family history of PD or RLS. The average age of onset of RLS was 61.7+/-10.8 years old. The mean global Pittsburgh Sleep Quality Index (PSQI) score of PD patients was significantly higher than the controls (9.1+/-4.5 vs 4.3+/-2.8, p<0.0001). All the seven components of PSQI in PD patients were significantly different from controls (p<0.0001). Multivariate analysis revealed that only Hoehn and Yahr staging correlated with the global PSQI score (p<0.0001). Similar results were obtained when we compared the PSQI score between PD patients without RLS with controls. Our case-control study demonstrated a weak association between RLS and PD. PD patients have significant poor quality of sleep, and this correlated with the severity of PD. RLS did not play an important role in sleep dysfunction in our PD cohort. A high index of suspicion for sleep problems in advanced PD patients is important as early management could improve their quality of life.