Oligodendrocytes, the myelinating cells of the central nervous system, have a characteristic morphology, whose full extent is revealed immunohistochemically by the expression of specific markers. Proteolipid protein (PLP) is regarded as a terminal differentiation marker of oligodendrocytes. By using PLP antibody and confocal microscopy, PLP expression in developing oligodendrocytes and the detailed three-dimensional morphology of oligodendrocytes were observed throughout early and late Xenopus laevis tadpole development. Premyelinating oligodendrocytes with radial processes were intensely stained with PLP antibody. The morphology of developing oligodendrocytes is comparable with that described in rodents. In Xenopus, the appearance of PLP- and MBP-positive oligodendrocytes is synchronized spatially and temporarily, revealing that PLP is also an early marker of developing oligodendrocytes. In addition, oligodendrocytes in early tadpole spinal cord are few in number but have a large cell body that is easily identified on a transverse section, revealing the relatively simple cytoarchitecture of this glial component. Xenopus spinal cord may therefore be useful as model system for studying the maturation of oligodendrocytes and the myelination process in situ.