The pathogenetic relationship of welding-related Parkinsonism (WP) and idiopathic Parkinson's disease (PD) is a matter of debate. In the present study, we compared transcranial sonography (TCS) findings in patients with WP and PD. Two male patients with WP, who had developed levodopa-resistant akinetic-rigid Parkinsonism without ongoing progression after having worked as welders for many years in Chilean mines in confined spaces without adequate ventilation, and three age-matched male patients with clinically definite akinetic-rigid PD were studied with TCS in a random order by two investigators blind to clinical diagnoses. In both WP patients, normal echogenicity of substantia nigra was found whereas all PD patients exhibited marked substantia nigra hyperechogenicity, previously reported as a characteristic TCS finding in idiopathic PD. In contrast, lenticular nucleus was hyperechogenic in both WP patients but only in one of the PD patients. TCS findings suggest a different pathophysiology of Parkinsonism in WP and PD patients.