Low body weight is a characteristic symptom of Parkinson's disease (PD), but the mechanism is unknown. To determine whether bulbar involvement is responsible for the weight loss, we compared the mean body weight (MBW), height, and body mass index (BMI) of 281 patients with PD and 86 patients with progressive supranuclear palsy (PSP). Although the patients with PSP had significantly worse dysphagia and dysarthria than the patients with PD, their MBW and BMI were not appreciably different. We conclude that bulbar dysfunction is not the reason for weight loss in PD.