Introduction: More recognition of myelinated nerve fibers of the extreme capsule inhuman brain. Materials and Methods: 10 adult normal human brains (20 hemispheres) from both sexes were studied using 15 am serial sections in all three cardinal planes after fixation and processing. These sections were stained by Klüver - Barrera and Heidenhain- Woelcke methods. Results: Fibers which originated from frontoparietal operculum entered the dorsalborder of the extreme capsule. Most of these fibers placed in lateral part of the extremecapsule terminated in dorsal part of insular gyri. A few of these fibers descended near the claustrum to reach to the temporal operculum, including the auditory area, andsuperior temporal gyrus. some of extreme capsule fibers terminated or originated from the claustrum. Some fibers exchanged between ventral part of superior insular gyrus and dorsal part of inferior temporal gyrus; in fact these fibers connected the adjacent insulargyri. Some of fibers originated from ventral part of superior insular gyrus decended near the claustrum and reached to temporal operculum and superior temporal gyrus. All of fibers came from ventral part of inferior insular gyrus as well as some fibers came from the claustrum reached to temporal operculum and superior temporal gyrus. Uncinateand inferior longitudinal fasciculi passed through the ventral part of extreme capsule. Some fibers interconnected external and extreme capsules through dorsal claustrum. Conclusion: Most of the extreme capsule fibers are association, although some of them are projectional. The associated fibers in the extreme capsule can be divided into three groups: 1) Long and well known association fibers, 2) Short association fibers, and 3) Association fibers which connect frontoparietal operculum with temporaloperculum. The authors believe that the latter group can be called "Intermediateassociation fibers".