Guided tissue regeneration (GTR) is effective in halting tissue and bone destruction and promoting new tissue and bone formation. Although the goal of complete and predictable regeneration still remains elusive, many techniques and materials have been developed that show good clinical and histologic outcomes. The most commonly used materials in GTR include bone replacement grafts from numerous sources, nonresorbable and bioabsorbable membranes, and recently growth hormones/cytokines and other host modulating factors. This article reviews the biologic rationale behind current techniques used for tissue/bone regeneration, reviews the most common materials and techniques, and attempts to explain the factors that influence the outcomes of these therapies.