Defects of the dura mater, which are a source of cerebral spinal fluid leakage, may be produced by trauma and otologic and neurosurgical operations. Proplast was evaluated as a graft material to close dural defects in three animal models (cats). For comparison, temporalis fascia was similarly evaluated in an additional three cats. Microsurgical techniques were utilized to close the defects, and both materials successfully prevented cerebral spinal fluid leakage. Proplast, however, was judged superior when studied microscopically at three months. There was ingrowth of living dura into the Proplast and no evidence of inflammatory reaction.