Cranioplasty performed after external decompression for brain swelling may be difficult because of the development of adhesions between the temporal muscle and the dura. Membranes composed of expanded polytetrafluoroethylene (ePTFE) were inserted at external decompression to prevent such adhesions. The ePTFE membranes were placed suturelessly between the temporal muscle and the dura, covering the proximal portion of the temporal muscle at the sphenoidal ridge and the dural suture line. In addition, part of the membrane was placed directly below the skin incision to allow easy visualization at subsequent cranioplasty in 10 patients. Cranioplasty was performed 38 to 126 days (mean 63.9 days) after external decompression. No adhesions were observed, either between the ePTFE membranes and the dura, or between the membranes and the temporal muscle. No temporal muscle and dural injuries occurred during cranioplasty, and no patient showed signs of infection. Mean operating time was 71.0 minutes and mean blood loss was 75.2 ml. Sutureless insertion of ePTFE membranes at external decompression increases the ease and safety of subsequent cranioplasty, decreases operating time and blood loss, and avoids injury to the temporal muscle and dura.