Residual pocket is a common problem post periodontal therapy and may lead to poor prognosis of intrabony defects. Guided tissue regeneration (GTR) with different materials has been shown a feasible and predictable way to reduce the depths of residual pockets. Efforts in choosing appropriate materials have also been made to achieve a balance between the outcome, efficiency and cost under the anatomical and surgical limitations. Calcium sulfate exists in great natural source and has a long hi story in medical use. In this paper, related reports of calcium sulfate in periodontal GTR will be discussed and two clinical cases will be presented.