Objectives: The purpose of this split-mouth study was to evaluate the clinical response of enamel matrix proteins (EMPs, Emdogain Gel) in intra-osseous defects with or without a combined application of a tetracycline-coated expanded polytetrafluoroethylene barrier membrane (e-PTFE, Gore-Tex). Methods: Twelve pairs of intra-osseous periodontal defects in 11 patients received the application of EMPs on the exposed root surface (EMP). One of the two defects received randomly, as an adjunct to EMP treatment, a tetracycline-coated e-PTFE membrane (MEMP). At baseline, 6- and 12-month probing pocket depth (PPD), clinical attachment level (CAL) and probing bone level (PBL) were measured. Results: After 12 months, the EMP defects showed a significant mean PPD reduction of 2.86 _ 0.75 mm, a mean gain in CAL of 1.28 _ 2.04 mm, a mean PBL gain of 1.63 _ 1.21mm and a mean increase of recession (REC) of 1.56 _ 2.30 mm. The MEMP defects showed a significant mean PPD reduction of 3.02 _ 1.55 mm, a mean gain in CAL of 1.65 _ 1.29 mm, a mean PBL gain of 1.58 _ 1.92mm and a mean increase of REC of 1.38 _ 1.63 mm. Except for significantly more post-operative discomfort at the MEMP sites, no significant differences were found between EMP and MEMP defects. Conclusion: Within the limits of this study, it is concluded that in the treatment of intra-osseous defects with EMP, the adjunctive use of a tetracycline-coated e-PTFE membrane failed to show more gain of CAL and PBL.