Differential diagnostic criteria of lateral amyotrophic sclerosis (LAS) and lateral amyotrophic sclerosis syndrome were elaborated on the basis of complex investigation, including EMG and blood plasma trace element analysis. Fifty-two patients (25 with LAS, 27 with LAS syndrome) have been examined, the diagnoses being established according to the World Neurologist Federation criteria. LAS syndrome was stipulated by a vascular spinal cord lesion-discircular myelopathy; in some cases vascular deficit was combined with an inherent narrowness of spinal cord channel. All patients were followed-up with a 6-month interval. The results of the study allow to differentiate LAS and LAS syndrome of vascular genesis, already during the first medical examination.