Brainstem and spinal pathways of untreated patients with idiopathic restless legs syndrome (RLS) were examined using magnetic resonance imaging (MRI), blink reflex, first and second exteroceptive suppression (ES1, ES2) of temporalis muscle, and H reflex. MRI of 25 patients elicited no structural lesions beyond age-related atrophy or white matter lesions on proton density- and T2-weighted coronal and axial images. All patients showed a normal latency of the soleus H reflex (mean +/- SD latency = 31.22 +/- 2.81 ms) and the H/M ratio was 48 +/- 17%. The duration and onset latency of the direct and indirect blink reflex responses were normal in all patients compared with those of controls (p > 0.5). There was no significant difference in ES1 and ES2 latencies or duration between patients and controls (p > 0.5). These results suggest that the etiology of RLS symptoms does not involve structural lesions.