This study investigated nerve regeneration through a pseudosynovial sheath in a primate. After resecting a 3-cm segment of the ulnar nerve at the elbow, the two ends of the divided nerve were placed at either end of the pseudo- synovial tube, positioning the nerve ends such that they were separated by a 3-cm gap. Histologic evaluation at 3, 5, 7, and 9 months demonstrated evidence of nerve regeneration across this gap. Nerve fiber diameter and density assessment demonstrated a maturation of the fiber pattern with time. The overall morphologic pattern of the regenerating nerve within the pseudosheath was that of multiple small fascicles, each within its own perineurial compartment. This pattern resembled neither the proximal nor distal nerve fascicular pattern.