The endoneurial extracellular matrix (ECM) is produced by Schwann cells and fibroblasts under the control of axons. Dorsal and ventral spinal roots contain different types of axons, but information is not available on differences in the composition of their ECM. A comparison was made of the intensity of immunofluorescence staining of chondroitin sulfate proteoglycan, fibronectin, tenascin and thrombospondin in the endoneurial ECM of rat dorsal and ventral spinal roots. Sections of dorsal and ventral roots were incubated simultaneously for indirect immunofluorescence detection of the epitopes studied. Brightness of immunofluorescence staining was assessed by computer-assisted image analysis using interactive segmentation of digitized images to select areas to be analyzed. Our results revealed quantitative differences in the composition of endoneurial ECM of spinal dorsal and ventral roots, probably due to the presence of different types of axons. The ECM composition of the endoneurium in dorsal and ventral roots may be related with the creation of extrinsic conditions that support differential regeneration of afferent and motor axons after injury.