Chondroitin sulfate proteoglycans (CSPGs) are macromolecules which regulate the structural organization of the extracellular matrix and can mediate cell migration and axonal growth. Here the spatiotemporal distribution of CSPGs in the central auditory system of rats was investigated using a polyclonal antiserum. In adult brains, CSPGs surrounded many neuronal cell bodies and proximal dendrites at all stations of the auditory pathway except the medial geniculate body. During development, CSPG expression became visible at postnatal day (P) 4 in the superior olivary complex, at P8 in the midbrain, and at P18 in the cortex. Immunoreactivity increased strongly until P12 in the brainstem and until P24 in the cortex. The adult-like pattern in the pontine nuclei, the midbrain, and the cortex was seen at P12, P29, and P35, respectively. The relatively late expression of strong immunoreactivity indicates that the CSPGs are involved in the maturation of axonal connections, but not in early processes such as cell migration or neurite outgrowth.