The characteristics of intrinsic muscle fibers in the anterior third of the adult rat tongue were studied employing light microscopy, SEM and high-resolution SEM (HRSEM) methods. For light microscopy, specimens were fixed in Bouin's solution and embedded in paraffin. In order to identify the muscle fibers and bundles of collagen fibers, frontal sections were stained with hematoxylin-eosin, azo-carmin and picro-sirius. The results showed that muscle fibers near the lamina propria are fixed with connective tissue, constituting several groups. The bundles of muscle fibers are arranged in longitudinal, vertical and transversal directions. For SEM, specimens were fixed in modified Karnovsky solution and freeze-fractured in liquid nitrogen revealed the collagen fibers and bundles of muscle fibers located in three-dimensional aspects. The samples treated in NaOH solution showed the original location of collagen fibers, constituting complex networks in three-dimensional SEM images. Under HRSEM, fractured specimens in DMSO revealed basement membrane of muscle cell containing sponge-like structures and networks of fine collagen fibrils. Cytoplasmic organelles, such as mitochondria with cristae mitochondriales and sarcoplasmic reticulum, were cleary seen in three-dimensional HRSEM images