Gastrointestinal symptoms such as nausea, abdominal pain, and bloating are frequent complaints of patients with Parkinson's disease (PD). It has been postulated that impaired gastrointestinal function may contribute to the development of motor fluctuations such as delay on and no on in patients with PD. Gastrointestinal impaired function and symptoms may be associated with the disease itself or secondary to levodopa treatment. Thus, we assessed gastric emptying (GE) and gastric motility in PD patients to examine the association between clinical status and gastric function. GE and antral contraction (frequency and amplitude) were evaluated by scintigraphy in 29 patients with mild PD (Hoehn and Yahr [H&Y] stage 1.0–2.0); 22 patients with moderate PD (H&Y stage 2.5–3.0); and 22 healthy volunteers, following the ingestion of a labeled standard meal. Gastric emptying (mean ± SD of T1/2) and antral contraction were not significantly different between patients with mild PD (63.4 ± 28.8 minutes) and moderate PD (54.7 ± 25.5 minutes). In the control group, GE was 43.4 ± 10.8 minutes (range 29.0 – 61.0 minutes). The prevalence of delayed emptying (>61 minutes) was not significantly different in patients with mild disease (48.3%) as compared with patients with moderate disease (36.4%). Antral contraction, both frequency and amplitude, were not significantly different between patients with mild and moderate PD throughout the entire 100 minutes of the study. Untreated patients (n = 28) had mean GE T1/2 of 59 ± 30.6 minutes. Patients with smooth response to levodopa showed slower GE (n = 10; 73.6 ± 25.3 minutes), while treated patients with motor response fluctuations when tested at the on state (n = 13), had much faster GE (49.3 ± 16.2 minutes). This shortened GE in the on state was similar to the GE of normal volunteers. We conclude that gastric emptying time in patients with PD was delayed compared with control volunteers. It was even slower in patients treated with levodopa. This effect of levodopa treatment was reversed to pseudonormalization (normal GE) at the advanced stages of the disease, when patients developed motor response fluctuation. Other clinical features of PD were not associated with delayed gastric emptying. © 2001 Movement Disorder Society.