The blood-spinal cord barrier (BSCB) of the spinal cord capillary consists of non-fenestrated endothelial cells with tight junctions, basal laminae, pericytes and astrocyte feet processes, referred to as a “neurovascular unit.” The primary function of the BSCB is the maintenance and control of homeostasis of the spinal cord parenchyma by the selective transport of molecules and cells from the systemic compartment. Dysfunction of the BSCB shows important function in the etiology or progression of several pathological conditions of the spinal cord, including amyotrophic lateral sclerosis (ALS). However, the role of BSCB in the pathogenesis of ALS is still unclear. Here the changes of BSCB in sporadic ALS patients were studied by electron microscopy to determine whether the BSCB is disrupted and involved in the pathogenesis of motor neuron degeneration. A total of 358 and 366 cross-sectioned capillaries were quantitatively examined in controls and ALS patients, respectively. The frequency of degenerated endothelia and pericytes, vacuolar changes of the cytoplasm in the endothelia and pericytes, and the replication of basement membranes was significantly higher in ALS patients than in the controls (P= 0.0175). The areas of the capillaries with diameters of ≤ 5 μm in the ALS patients were significantly smaller than those in the controls (P= 0.0124). The frequency of collagen fiber content of more than a moderate degree around the perivascular space was significantly higher in the ALS patients compared to the controls (P= 0.048), although there was no significant difference in the mild degree of accumulation of collagen fibers. Thus, the BSCB may be disrupted in sporadic ALS patients due to increased permeability and reduced microcirculation, leading to motor neuron degeneration and to the progression of the disease.