α-Dystroglycan, which is a cell surface component of dystroglycan complex, is known to bind laminin in basal lamina of muscle cells and Schwann cells. We found previously that a novel O-glycan, Siaα2-3Galβ1-4GlcNAcβ1-2Man, is the major oligosaccharide in bovine peripheral nerve α-dystroglycan, and that this structure might mediate the binding of laminin. In order to determine whether this structure is specific for peripheral nerve α-dystroglycan or present on different forms of α-dystroglycan, we analyzed the structures of the sialylated O-glycans of rabbit skeletal muscle α-dystroglycan. Their structures were elucidated to be a mixture of a core 1 O-glycan and the same O-mannosyl glycan that we found in bovine peripheral nerve. These results indicate that α-dystroglycan in different species and tissues share a common structure of its major O-linked acidic carbohydrate, suggesting its relevance to the basic functional role of α-dystroglycan.