This study compared the natures of various guided tissue regeneration (GTR) membranes impregnated with amoxicillin or tetracycline. Whether the antibiotics-loaded membranes enhance the attachment of the periodontal ligament cells in the presence of oral pathogens was further analyzed. S mutans and A actinomycetemcomitans diminished the attachment of periodontal ligament cells onto the membranes as evaluated by SEM analysis. These bacterial effects on cellular attachment could be reversed using the antibiotics-loaded membranes. The information obtained in this study is valuable for the future application of antibiotics-loaded membranes during GTR therapy.